Let x = the number of girls and (x + 15) = the number of boys
The ratio of girls to boys is 2:3, so we can set up the following equation:
x/(x + 15) = 2/3
3x = 2(x + 15) = 2x + 30
3x = 2x + 30
x = 30
There are 30 girls and 30 + 15 = 45 boys on the track team