Tom scored an average of 87 points on his last 4 math tests. his average score for the next 2 math tests was 90 points. what was tom's average score for all 6 tests?

Assuming equal weight for each test,

Average score = total score/number of tests

Total score = 4 tests at 87 + 2 tests at 90 = 4*87+2*90 = 348+180 = 528 points

Number of tests  = 4+2 = 6 tests

Average score = total score/number of tests = 528/6= 88 points