What is the constant of variation, k , of the line y is equal to k x through 3 comma 18 and 5 comma 30 ?

For a line of the form y = kx, the constant of variation is k = y/x. Using the point (3, 18), k = 18/3 = 6; the other point gives 30/5 = 6 as well. The correct choice is 6.

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