Trinity’s scores on the first 4 tests were 97, 92, 76, and 89. What is the minimum score Trinity needs to make on the fifth test so that her mean test score is at least 85?

The answer should be 71

71

Explanation:

Let’s use x for what the fifth test will be called.

1: The mean test score = (97 + 92 + 76 + 89 + x) • 5 = 85

^ the 85 is there because that’s the number she at least wants for her mean test score.

2: (354 + x) • 5 = 85

3: Multiply 5 • x to get it out of the parenthesis then do the same with the other side (85).

4: 354 + x = 425

5: 425 - 354 = 71

6: x = 71

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2