diff --git a/03_Day_Operators/03_operators.md b/03_Day_Operators/03_operators.md
index 0fcfeb99..987a1180 100644
--- a/03_Day_Operators/03_operators.md
+++ b/03_Day_Operators/03_operators.md
@@ -75,7 +75,7 @@ print('Division: ', 7 / 2)        # 3.5
 print('Division without the remainder: ', 7 // 2)   # 3,  gives without the floating number or without the remaining
 print ('Division without the remainder: ',7 // 3)   # 2
 print('Modulus: ', 3 % 2)         # 1, Gives the remainder
-print('Exponentiation: ', 2 ** 3) # 9 it means 2 * 2 * 2
+print('Exponentiation: ', 2 ** 3) # 8 it means 2 * 2 * 2
 ```
 
 **Example:Floats**
diff --git a/03_Day_Operators/day-3.py b/03_Day_Operators/day-3.py
index b1402885..c984a82c 100644
--- a/03_Day_Operators/day-3.py
+++ b/03_Day_Operators/day-3.py
@@ -10,7 +10,7 @@
 print('Division without the remainder: ', 7 // 2)   # gives without the floating number or without the remaining
 print('Modulus: ', 3 % 2)                           # Gives the remainder
 print ('Division without the remainder: ', 7 // 3)
-print('Exponential: ', 3 ** 2)                     # it means 3 * 3
+print('Exponential: ', 2 ** 3)                     # 8 it means 2 * 2 * 2
 
 # Floating numbers
 print('Floating Number,PI', 3.14)
diff --git a/07_Day_Sets/07_sets.md b/07_Day_Sets/07_sets.md
index 3c61dd07..52b18e5a 100644
--- a/07_Day_Sets/07_sets.md
+++ b/07_Day_Sets/07_sets.md
@@ -226,7 +226,7 @@ fruits = set(fruits) # {'mango', 'lemon', 'banana', 'orange'}
 
 ### Joining Sets
 
-We can join two sets using the _union()_ or _update()_ method.
+We can join two sets using the _union()_ or _update()_ method or _|_ symbol .
 
 - Union
   This method returns a new set
@@ -235,7 +235,7 @@ We can join two sets using the _union()_ or _update()_ method.
 # syntax
 st1 = {'item1', 'item2', 'item3', 'item4'}
 st2 = {'item5', 'item6', 'item7', 'item8'}
-st3 = st1.union(st2)
+st3 = st1.union(st2) #st3 = st1 | st2
 ```
 
 **Example:**
@@ -244,6 +244,7 @@ st3 = st1.union(st2)
 fruits = {'banana', 'orange', 'mango', 'lemon'}
 vegetables = {'tomato', 'potato', 'cabbage','onion', 'carrot'}
 print(fruits.union(vegetables)) # {'lemon', 'carrot', 'tomato', 'banana', 'mango', 'orange', 'cabbage', 'potato', 'onion'}
+# or using this : print(fruits | vegetables)
 ```
 
 - Update
@@ -267,13 +268,14 @@ print(fruits) # {'lemon', 'carrot', 'tomato', 'banana', 'mango', 'orange', 'cabb
 
 ### Finding Intersection Items
 
-Intersection returns a set of items which are in both the sets. See the example
+Intersection returns a set of items which are in both the sets or using _&_ symbol. See the example
 
 ```py
 # syntax
 st1 = {'item1', 'item2', 'item3', 'item4'}
 st2 = {'item3', 'item2'}
 st1.intersection(st2) # {'item3', 'item2'}
+# or using thia : st1 & st2
 ```
 
 **Example:**
@@ -286,6 +288,7 @@ whole_numbers.intersection(even_numbers) # {0, 2, 4, 6, 8, 10}
 python = {'p', 'y', 't', 'h', 'o','n'}
 dragon = {'d', 'r', 'a', 'g', 'o','n'}
 python.intersection(dragon)     # {'o', 'n'}
+# python & dragon
 ```
 
 ### Checking Subset and Super Set
@@ -318,14 +321,14 @@ python.issubset(dragon)     # False
 
 ### Checking the Difference Between Two Sets
 
-It returns the difference between two sets.
+It returns the difference between two sets or using _-_ symbol .
 
 ```py
 # syntax
 st1 = {'item1', 'item2', 'item3', 'item4'}
 st2 = {'item2', 'item3'}
-st2.difference(st1) # set()
-st1.difference(st2) # {'item1', 'item4'} => st1\st2
+st2.difference(st1) # set() : st2 - st1
+st1.difference(st2) # {'item1', 'item4'} => st1\st2  : st2 - st1
 ```
 
 **Example:**
@@ -338,19 +341,21 @@ whole_numbers.difference(even_numbers) # {1, 3, 5, 7, 9}
 python = {'p', 'y', 't', 'o','n'}
 dragon = {'d', 'r', 'a', 'g', 'o','n'}
 python.difference(dragon)     # {'p', 'y', 't'}  - the result is unordered (characteristic of sets)
+# python - dragon
 dragon.difference(python)     # {'d', 'r', 'a', 'g'}
+# dragon - python
 ```
 
 ### Finding Symmetric Difference Between Two Sets
 
-It returns the symmetric difference between two sets. It means that it returns a set that contains all items from both sets, except items that are present in both sets, mathematically: (A\B) ∪ (B\A)
+It returns the symmetric difference between two sets. It means that it returns a set that contains all items from both sets, except items that are present in both sets, mathematically: (A\B) ∪ (B\A) or using _^_ symbol
 
 ```py
 # syntax
 st1 = {'item1', 'item2', 'item3', 'item4'}
 st2 = {'item2', 'item3'}
 # it means (A\B)∪(B\A)
-st2.symmetric_difference(st1) # {'item1', 'item4'}
+st2.symmetric_difference(st1) # {'item1', 'item4'} : st2 ^ st1
 ```
 
 **Example:**
@@ -363,6 +368,7 @@ whole_numbers.symmetric_difference(some_numbers) # {0, 6, 7, 8, 9, 10}
 python = {'p', 'y', 't', 'h', 'o','n'}
 dragon = {'d', 'r', 'a', 'g', 'o','n'}
 python.symmetric_difference(dragon)  # {'r', 't', 'p', 'y', 'g', 'a', 'd', 'h'}
+# python ^ dragon
 ```
 
 ### Joining Sets
diff --git a/10_Day_Loops/10_loops.md b/10_Day_Loops/10_loops.md
index f03265a9..f8a98344 100644
--- a/10_Day_Loops/10_loops.md
+++ b/10_Day_Loops/10_loops.md
@@ -302,6 +302,10 @@ lst = list(range(0,11,2))
 print(lst) # [0, 2, 4, 6, 8, 10]
 st = set(range(0,11,2))
 print(st) #  {0, 2, 4, 6, 8, 10}
+
+# for backward from start to end 
+lst = list(range(11,0,-2))
+print(lst) # [11,9,7,5,3,1]
 ```
 
 ```py
diff --git a/11_Day_Functions/11_functions.md b/11_Day_Functions/11_functions.md
index 2a0ad39b..adb308c2 100644
--- a/11_Day_Functions/11_functions.md
+++ b/11_Day_Functions/11_functions.md
@@ -369,7 +369,7 @@ def square_number (n):
     return n * n
 def do_something(f, x):
     return f(x)
-print(do_something(square_number, 3)) # 27
+print(do_something(square_number, 3)) # 9
 ```
 
 🌕 You achieved quite a lot so far.  Keep going! You have just completed day 11 challenges and you are 11 steps a head in to your way to greatness. Now do some exercises for your brain and muscles.