Answer:
I guess that the purchase is at random, then let's see the possible options:
5 diet drinks.
10 regular drinks.
Total drinks = 15
6 bags of fat-free chips
10 bags of regular chips.
Total chips = 16.
Probability of buying at random, a regular drink is equal to the number of regular drinks divided the total number of drinks:
p1 = 5/15 = 1/3
Probability of buying at random a regular bag of chips, we use the same reasoning as before.
p2 = 6/16 = 3/8
The joint probability will be equal to the product of the individual probabilities:
P = p1*p2 = (1/3)*(3/8) = 1/8.