nguyenpatrick23
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# On his first two social studies tests, Billy made an 86 and a 93. What grade must Billy make on the third test to have an average of 90 for all three tests? a. 91 c. 85 b. 87 d. 90

We know that there are 3 tests and he's already taken 2. The definition of average it to add up all the scores and divide by how many tests there are. setup: $\frac{86 + 93 + n}{3} = 90$ multiply each side by 3 : 86 + 93 + n = 270 Simplify: 179 + n = 270 Subtract 179 from each side: n = 91 so A