Answer:
400 boys
Explanation:
First use the fraction along with the given information (240 girls)
If 5/8 of the school are boys, then that means 3/8 of the school's students are girls. 3/8 happen to be equal to 240, which means we can conclude that 1/8 is equivilant to 240/3 = 80
80 multiplied by 5 = 400
There are 400 boys in the school. (640 total students in school)
Tip: Easy way to check answer is by putting the boys over the total students to find the ratio, and if it matches, your answer is correct. 400/640 = 0.625, which equals 5/8
Hope this helps :)