I think the correct one is b but I’m not sure
If it is in the form of y=mx+b then the answer would be y=34x+60

a. "Chocolate" and "Adults" (whatever those mean) will be independent as long as

"Chocolate" has the marginal distribution given by the second column, with a total probability of

. Similarly, "Adults" has the marginal distribution described by the third row, so that

. Then

Meanwhile, the joint probability of "Chocolate" and "Adults" is given by the cell in the corresponding row/column, with

.
The probabilities match, so these events are indeed independent.
Parts (b) and (c) are checked similarly.
b. Yes;


c. Yes;

5a+2a(5−b)
Distribute:
=5a+(2a)(5)+(2a)(−b)
=5a+10a+−2ab
Combine Like Terms:
=5a+10a+−2ab
=(−2ab)+(5a+10a)
=−2ab+15a