Let X be the random variable representing the number
of coins that Matt set aside after three flips.

We have to run n from 0 to 100 and m from 0 to (100-n),
Find the binomial law, then compute the mean like this:

Hope this gives a hint.
The "mean" is the same thing as the "average".
To get the average, you add up all the numbers on the list,
then divide the big sum by the number of items on the list.
If there are 100 numbers on the list, then in order to find their average,
you would add up all 100 numbers, then divide the big sum by 100.
If you wound up with an average of 51.18, then you must have had
5,118 just before you divided it by 100. So the big sum is 5,118.
Answer:
0.25
Step-by-step explanation:
The total number of marbles is 2 + 2 + 3+ 5 = 12
the number of green ones is 3
So the probability of green = 3/12 = 1/4 = 0.25