Maria's test scores are 80, 70, and 90. What score does she need to get on a fourth test so that her average score for the four tests is exactly 85?
She needs to have a total of 4*85=<<4*85=340>>340 points over the four tests.
She has 80+70+90=<<80+70+90=240>>240 points so far.
She needs 340-240=<<340-240=100>>100 on the fourth test.
#### 100