To earn a “B” in a mathematics course your average score must be at least 80. If you earn a 70, 75 and 82 on the first three exams, what must you score on the 4th exam to earn a “B”?

A good way to do these sort of problems is to think backwards. So you need an average of 80 for all four of your tests. So all you need to do is multiply 80 by 4 to get 320 and subtract the three test scores. So 320 - 70 - 75 - 82 = 93. So the next score would be 93. Hope this helps