There are 12 boys and 15 girls in your class four new students, 3 boys and 1 girl, join your class compare the ratio of to girls before and after the new students enrolled

Before the new kids the ratio of girls to boys is 15:12 because there are 15 girls and 12 boys now you can simplify by dividing 15 by 3 and 12 by 3 to get 5:4 as your simplified ratio. As far as after the new kids. Since there is 1 new girl you do 15+1 to get 16 and there are 3 new boys so you do 12+3 to get 15 now 16:15 is already in simplest form so your answer is:

Before: 15:12 simplified as 5:4
After 16:15

Hope this helps.