If we divide the amount boys OR girls ( depending on which gender) after the toal and move the decimal to the right twice after dividing) we will get our answer.
Formula:
(Amount of Boy or girls) = x
X/28
So since we are trying to get the percentages of boys, we will replace X with the amount of boys
21/28 = .75 ( then move the decimal to the right TWICE) = 75
Then you should get your percentages: 75% Also if your lookings for girls percentages, you basically subtract 75 ( boys percentages) with the total percentages ( 100) then you should get your answer for the girls: 25%