5/8 of the students in my class were boys.

When 6 girls joined the class, the number of boys equaled the number of girls.
How many students were in my class then?

"What's the formula for this problem?"

1 answer

b = (5/8) s
so
g = (3/8) s
now g = (3/8) s + 6
and number of students = s + 6

b = 5/8 s = (3/8)s +6
so
(2/8)s = 6
s = 24

that was original s
s+6 = new total = 30