Question 899533
There are going to be 6 tests in total, all averaging out to be 85. So the sum of these tests is 85*6 = 510

These tests are 89+92+78+83+83+x, where x represents the 6th test.

89+92+78+83+83+x = 510

425 + x = 510

x = 85

He must get a 85%.