Answer:
Step-by-step explanation: If w is hours at Westside, then (18-w) is the number of hours taken at Pinewood.
Cost to westside = 98w. Cost to Pinewood = 115(18-w).
Total cost = 98w + 115(18 - w) = 2070 - 17w.
[I guess there should be some constraints like 0 > w > 18]
I put it as "greater than" rather than "greater than or equal" because the problem states he takes classes at both schools, hence he has to take at least something at Westside, and similarly he has to take something at Pinewood so he would not take all 18 hours at Westside.