Your test average is 86 after taking three tests. you remember that two of your scores were 88 and 83. what was your score on the third test? show on how you got the answer so i can understand it better.

(88 + 83 + x) / 3 = 86
(171 + x) / 3 = 86...multiply both sides by 3
171 + x = 86 * 3
171 + x = 258
x = 258 - 171
x = 87 <== ur other test score

** to find the average, u would add up all of ur test scores and divide by how many tests there were.