How do you calculate to get a percentage?

It is really simple ! For an example : If kim got 15 wrong out of 72 questions , its 72 - 15 = 57 , so what you do is subtract the amount wrong of the amount taken away by the total and you divide that by your total , so 57/72 = 0.7916 and you x by 100 so 0.7916 x 100 = 79.16 , so Kim got a 79 on her test !