J=15b/10g
S=21b/g w/ the ratio 3/2 (15/10=3/2)
1) Form an equation (21/g=3/2).
2) Since you are trying to find the denominator, multiply 3/2 so that the numerators are the same (3×7=21 2×7=14).
3) The answer will be whatever the denominator is at the end.
The answer is there are 14 girls in Steven's class.