Update writingIonicFormulas2.pg

Author: stebryan

ProblemLibrary/setCH151_Nomenclature/writingIonicFormulas2.pg

@@ -149,7 +149,7 @@ Write the formula for the following names.
 
 Use [`CH_3COO^{-}`] for acetate in this problem.  This would be entered as CH_3COO in the formula. 
 
-example:  manganese(IV) sulfide  `MnS_{2}`
+example:  manganese(IV) sulfide  [`MnS_{2}`]
 
 a. [$answ[0]] [____________________]{$finalAns[0]}