answer
94
set up equations
average = total points / number of tests
total points = test1 + test2 + test3 + test4+ test5
total points = 88 + 94 +89 + 85 + test5
total points = 356 + test5
plug total points into first eqation and rearrange
average = total points / number of tests
average = (356 + test5)/number of tests
average * number of tests = 356 + test5
test5 = average * number of tests - 356
plug in values for average and number of tests
test5 = average * number of tests - 356
test5 = 90 * 5 - 356
test5 = 94
