The ratio of boys to girls in 9 to 6 meaning for every 9 boys there are 6 girls or for every 6 girls there are 9 boys.
To find the number of girls, you first find how many times 9 boys goes into 36.
So 36 / 9 = 4
Every time there is 9 boys, there is 6 girls according to the question.
So now you take 4 and multiply it by the number of girls in the ratio.
So 4 x 6 = 24
24 girls in the answer.