Final answer:
To solve for y in a direct variation when x=20, use the found constant of proportionality 1.5 (from the given y=22.5 when x=15) and multiply it by 20 to get y=30 (Option C).
Step-by-step explanation:
If y varies directly as x, it means that y = kx, where k is the constant of proportionality. Given that y = 22.5 when x = 15, we can find the constant k by dividing y by x: k = 22.5 / 15 = 1.5. Therefore, the equation relating y and x is y = 1.5x.
To find y when x = 20, we substitute x into the equation: y = 1.5(20) = 30. Hence, the value of y when x = 20 is 30, which is option C.