There are 20 chips total.

a) Since there are 2 white chips out of 20 total chips, you have a 2/20 (or 1/10 = 0.10 = 10%) chance of picking a white chip.

For the next three questions, it's important to notice that the question says that after the first chip is drawn, it is put back in the urn before the second chip is drawn. That means that (1) the outcome of the first drawing doesn't affect the second, and (2) there are still 20 chips left in the urn, in the same proportions, for the second drawing.

b) In part a, we saw that there is a 0.10 chance of drawing a white chip. Similarly, there is a 8/20 = 0.40 chance of drawing a red chip.

To get the probability of drawing a white chip and a red chip, multiply the probabilities:

(0.10)(0.40) = 0.04 = 4%

c) Like in part b, we're going to multiply the probabilities. For each drawing, there is a 10/20 = 0.50 chance of picking a green chip. So, the probability of drawing 2 green chips is:

(0.50)(0.50) = 0.25 = 25%

d) Since, after drawing the first chip, you put it back in the urn, the outcome of the first drawing cannot affect the outcome of the second. So, no matter what happens in the first drawing, the chances of drawing a red chip are 8/20 = 0.40 = 40%.