Answer:
18
Explanation:
24/4 is equal to 6. This is the factor we can multiply by 3, which would be 18. Here's a more mathematical setup, where x is the unknown number of boys:
4 24
----- = --------
3 x
You can use cross-products or the "butterfly" method by multiplying 3 and 24 equal to 4x.
72 = 4x
x = 18