Y = kx We have to find k value, so lets say x is euros and y is American dollars so we have 9 = k(8) k = 1.125 so the equation will be y = 1.125x to prove it use another value given y = 1.125x y = 1.125 (24) y = 27 Thus 24 euros is 27 dollars. Hence the equation y =1.125x is correct.