I am really confused with a probability question and I would really appreciate your help.

Question: a) If the six-face dice is numbered by 1, 2, 3, 4, 5, and 6, but the eight-face dice is numbered by 1, 2, 3, 4, 5, 6, 6, and 6, what is the expected number if you roll each type of dice many times, respectively?

In this question, I did my calculations and I got an answer: E(X+Y)= E(X)+E(Y) = 3.5 + 4.125= 7.625. However, I am not very sure about it, because the question is not very clear to me. for example, do I have to find the sum value or the expected value for each die?

What really confuses me is part b)

Now if you randomly pick one dice from a black box with two six-face dices and one eight-face dice, what is the expected number you can roll?

Thank you!