If y varies directly as x and y = 15 when x = 5,what is the value of y when x = 6?

Direct variation means y = kx for a constant k. Using y = 15 when x = 5 gives k = 15 ÷ 5 = 3. When x = 6, y = 3 × 6 = 18, so the correct choice is 18.

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