Skylar's grades on four math tests are 85, 78, 77, and 69. What does Skylar need to score on the next test in order to have a mean score of 80? A) 83. B) 90. C) 91
(85 + 78 + 77 + 69 + x) / 5 = 80 (309 + x)/5 = 80 309 + x = 80 * 5 309 + x = 400 x = 400 - 309 x = 91 <== skylar needs to score a 91 to have an average of 80
