Maria has test grades of 78%, 87%, and 89%. What must she score on her next test to attain an average of at least an 85%? (state an inequality and solve it)

Question

im very confused about this problem pls help

Answer 1

Let X be her next score then (78+87+89+X)/4 percent is the average, which must be at least 85%, therefore (254+X)/4≥85. Multiply through by 4: 254+X≥340 and X≥340-254, so X≥86%.

She must score at least 86% on the next test to average 85% over four tests.