First thing you need to do is find your k in y = kx
So to do that insert 18 for x and 6 for y and then solve for k y = kx 6 = k18 6/18 = k18 /18 1 / 3 = k k = 1 /3 So now that we know what k is we can find x when y = 10. Once again insert the numbers we know. We know k = 1/3 and y = 10 and we need to find x y = kx 10 = (1/3)x 3* 10 = 3*(1/3)x 30 = x x = 30