9514 1404 393
Answer:
a. correct
b. 3 for $315; 5 for $485
Explanation:
You have correctly solved for x, the number of ski trips. As a practical matter, the formula is easier to use if you don't have to deal with mixed numbers or the odd fraction:

Use that formula to find the number of ski trips for each of the given amounts.
x = (315 -60)/85 = 255/85 = 3 trips
x = (485 -60)/85 = 425/85 = 5 trips