Question

tom scores 83,88,75, and 90 on the first 4 tests in algebra. what does he need to get on the 5th test to have an average of 85?

Answer 1

Assuming that the total possible score on each test, then the total possible points for 5 tests is 100.

0.85 * 500 = 425

He has a total of 336 points now.

425 - 336 = 89

Answer 2

You can also do this problem this way:
(83+88+75+90+x)/5=85