Hey there!
When dealing with percent word problems, the word "is" means equals. Let's see what we can do with your problem.
If the small school had 60% boys, it will have 40% girls. The number of boys is 48, which should equal 60% of the total, which we can model below, with t representing the total number of kids. In decimal form, 60% is 0.6.
0.6t=48
We divide both sides by 0.6.
t=80
Therefore, there are 80 total kids at the school.
We can also check our answer below.
BOYS: 0.6(80)= 48
GIRLS: 0.4(80)=32
48+32=80
I hope that this helps!