Tiny fix error "SyntaxError: invalid escape sequence '\%'"

[fzyzcjy]

The original code gives syntax error:

E     File "math_equivalence.py", line 110
E       string = string.replace("\%", "")
E                               ^^^^
E   SyntaxError: invalid escape sequence '\%'

I guess it means "%" so made this tiny change. Please correct me if I am wrong!