Question 442917
A teacher told Melinda that she has a course average of 78 based on her six math tests.
 When she got home, she found 5 of her tests with scores of 87, 63, 79, 71, and 96.
 She couldn't find the sixth test. What score did she obtain on that test?
;
Let x = score on the lost test
:
{{{(x+87+63+79+71+96)/6}}} = 78
:
{{{(x+396)/6}}} = 78
Multiply both sides by 6
x + 396 = 6(78)
x + 396 = 468
x = 468 - 396
x = 72 is the score of the lost test