Direct, Inverse, and Joint Variation - Direct variation A variable y varies directly with a variable x if the ratio Z remains constant. x Equivalently, y varies directly with x if we have the following. )2 = kx for some (nonzero) constant k Suppose thaty varies directly_ with x, and y = 27 when x = 3. (a) Write a direct variation equation that relates x and y . Equation: III (b) Find y when x = 5 . y=|]