Explanation:
I'll try:
7 boys choose 5 = 7! / (5!2!) = 21 ways
4 girls choose 2 = 4 ! / (2! 2!) = 6 ways
6 x 21 = 126 ways to choose 5 boys and 2 girls
11 cats total choose 7 = 11! /( 7! 4!) = 330 ways to choose 7 cats
126 of these will be 5 boys and 2 girls
126 out of 330 = 126/330 = .382