Question

Shelly's scores on her first two tests in Algebra were 72 and 89. What will she need to make on the third test to have an average of at least 80?

Answer 1

(72+89+x)/3=80

x=79

Answer 2

Average means adding up the scores and dividing by the number of scores, e.g.:
\[\frac{test_{1}+test_{2}+test_{3}}{\text{# of tests}}\]