As y varies directly with x, there is a proportionality constant. As x increases by that certain constant, y also increases. We equate: y = kx where k = proportionality constant. Given the condition, y = 5 when x = 4, then we solve for k: 5 = k(4) k = 5/4 or 1.25 When y = 8, then 8 = (5/4)(x) x = 8/(5/4) = (8)(4/5) = 32/5 or 6.4 (ANSWER)
