Emily earned a grade of 80% on a math test that had 20 problems. How many problems on this test did she answer correctly? If John got 7 problems incorrect on the same test, what was his grade?

Someone getting all 20 problems correct would earn a grade of 100%. Thus, each correct question counts 5%.

If Emily earned 80%, then the number of problems she got correct was (80% / 100%).

Simplify this result. It represents the fraction of 20 questions that Emily got correct. Multiply your result by 20 to find the actual number of questions that E. got correct.

0.8*20 = 16 problems answered correctly

If John got 7 problems wrong, then he got 14 problems right.

14/20 = 0.7

Now, convert 0.7 into a percentage.