The smaller grade is 36. The larger grade is 99.
Work Step by Step
Let X represent the lowest grade. Since X is the lowest grade, three times the lowest grade means 3 $\times$ X = 3X. 9 points less than three times the lowest grade means 3X - 9 The sum of the two grades was 135, so we can set up the following equation: X + 3X - 9 = 135 4X - 9 = 135 Add 9 to both sides 4X = 144 Divide both sides by 4 X = 36 Since X = 36, 3X - 9 = 99