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.

# Answer

100
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
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?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
100
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?
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