7. A student has received scores of 88, 82, and 84 on three quizzes. If tests count twice as much as quizzes, what is the lowest score the student can get on the next test to achieve an average score of at least 70?

Question

A. 13

B. 48

C. 70

D. 96

The correct answer is B, but I would like an explanation on how to get the right answer and how to set up the equation for a problem like this in the future. Thanks.

Answer 1

since tests count twice, add them twice. The total points must be the same as 5 scores of 70:

88+82+84+2x = 70*5
x = 48