When 18 boys joined a group of y students, the ratio of boys to girls in the group became 4:5 write an algebraic expression for the number of girls in terms of y.

Question

I don't understand at all

Answer 1

Altogether there are y+18

The ratio of boys to girls is 4:5

So there are 4(y+18)/9 boys and 5(y+18)/9 girls