Part A: About 0.21
We will put the wanted outcome (yellow pieces of candy) over the total number of possible outcomes (total pieces of candy).
About 0.21
Part B: About 50
First we will do the same as we did with the yellow pieces of candy, wanted outcomes over possible outcomes.
0.25
Now, we will multiply the total 200 pieces by 0.25 since 0.25 of them are estimated to be green.
200 * 0.25 = 50
I estimate about 50 of the pieces to be green.