Donna's average mark out of three tests is 84 out of 100. Her highest mark was one and one quarter times her lowest mark. The middle mark was 81. What were Donna's marks on the three tests?

Question

Write an algebraic expression

Answer 1

Donna had a total score of 84*3=252 on her three exams. One score was 81. So the total of the other two grades must be 252-81 = 171

Let r = lowest score. So highest score is 1.25r

So r + 1.25r = 2.25 r = 171. Then r = 171/2.25 = 76

171-76=95.

The three grades are 76, 81 and 95