Answer :
Answer: X=18
Step-by-step explanation:
let the numbers of girls be X
total in class = X + 12
number of students who do not volunteer
= (x + 12)/2
but this is 15
(x+12)/2 = 15
x+12 = 30
x = 18
So there are 18 girls in the class.
I hope this helped :)