Hassan has a bag which contains 20 coloured discs. He randomly chose three discs from the bag and found that two were red and one was white.

a) Based on this sample, how many of each coloured disc are in the bag?

b) Hassan returned the three discs to the bag and then randomly seleceted another three. This time he selected two whites and one red. How many of each coloured disc do you think are in the bag?

---> Please help me on how to solve these questions... Thank you