Answer:
I dont give you the answer right away so you will read what i write and fully understand :D
Step-by-step explanation:
We are picking 3 balls from 30 balls, so its C(30,3) because the order of picking the balls doesnt matter. We also need to pick 2 balls from 20 balls, which is C(20,2). So the answer is C(30,3) * C(20,2).