There are 25 students.
Let g = girls, and b = boys
g = 1/2b + 10
g + b = 25
Plug in 1/2b + 10 for g
(1/2b + 10) + b = 25
3/2b + 10 = 25
isolate the b, subtract 10 from both sides, and then multiply by 2/3
3/2b + 10 (-10) = 25 (-10)
3/2b = 15
(3/2b)/(2/3) = 15(2/3)
b = 30/3
b = 10
Subtract 10 from 25 to get the number of girls
25 - 10 = 15
g = 15
There are 10 boys in the class.
hope this helps