Each jacket costs $26.50 so x is the variable to depict how many jackets she is buying because it does not tell us in the question. There is a one-time fee of $15.99 so that is added on to the total to find the total cost which is y.
since student A and student B are independent of each other, we multiply their individual probabilities to get the probability of both solving the problem
A * B
= 0.9 * 0.6
= 0.54
there is a 0.54 probability that both will solve the problem
