Question

Lucy wants to be exempt from her semester exam. In order for that to happen, she has to average an 85 over 3 test grades. Her first 2 test grades were 81 and 86. What does Lucy need to make on her third test in order to have an exact average of 85 and be exempt from her exam?
Steve
total points for an 85 average: 85*3 = 255

Points so far: 81+86 = 167

So, haw many does she still need?
Ms. Sue
(85 * 3) - (81 + 86) = ?