9,3 + 5,7 + 15 = 30 / 11,3 + 3,7 +15 = 30
Reason:
In some non English speaking countries, they use comma in place of decimal. For example you can take countries like France and Italy. Here is a link to clarify your doubt: Math Forum - Ask Dr. Math
Also, I have used commas to use the characters you have provided in the question itself.