25% is equal to 1/4 correct? (It is :D) So divide 972/4 to know what 25% of the school's population is. 972/4 = 243. So then 243 is 25% of the students. To get the 25% increase add 972 (for the students that will be back next year) and 243 (for the new students). I may have explained this in a really detailed way but it isn't that hard when you think about it!