How do I solve this?

Question

Ami’s scores on the first 4 tests were 87,92,76, and 89. What is the minimum score she needs on the fifth test so her average is at least an 80?

Answer 1

(87+92+76+89+ x)/5 = 80

344/5 + x/5 = 80

x/5 = 80-344/5

x = 400-344 = 56

5th test score has to be at least 56 to get at least an 80 average