Thomas needs a b in his class. his current test scores are 88, 83, 86 and 72. his final exam is worth 3 test scores. In order to ear a b Thomas average must lie between 80 and 89 inclusive. what range of scores can Thomas receive on the final to earn a b in the class?

Answer 1

80 ≤ [(88 + 83 + 86 + 72 + 3x) / 7] ≤ 89

Answer 2

80≤329+3x/7≤89
Multiply everything by "7"
560≤329+3x≤623
Subtract everything by "329"
231≤3x≤294
Divide everything by "3"
77≤x≤42

Thomas has to receive at least a 77.