David’s scores on the first three of four 100-point math tests were 86, 92, and 89. What score does he need on his fourth math test to ensure an average score of at least 90?

A) X ≥ 89
B) X ≥ 93
C) X ≥ 78
D) X ≥ 90

Question

David’s scores on the first three of four 100-point math tests were 86, 92, and 89. What score does he need on his fourth math test to ensure an average score of at least 90? 

A) X ≥ 89
B) X ≥ 93
C) X ≥ 78
D) X ≥ 90

kropot72 · Answer

Let the required minimum score be x.
86 + 92 + 89 + x = 90 * 4 ...............(1)
Now you need to solve equation (1) to find x. Can you do that?

anonymous · Answer

x=93 ?

kropot72 · Answer

Correct. So can you see the correct choice of answer now?