Question

A box contains 8 white balls, 7 black and 4 red. How many red balls must be added to the box so that the probability is 3/4? How many black balls need to be added so that it is 1/4?
Thanks I have a mental block with this.

Answer 1

probability of what?

Answer 2

Sorry...
so that the probability of drawing a red ball is 3/4

so that the probability of drawing a white ball is 1/4