Melvina's age is = x, Bettina's age is = 3x the equation is x + 20 = 3x - 20 subtract 3x from both sides -(3x) + x +20 = 3x - 20 - (3x) -2x + 20 = -20 subtract 20 from both sides -2x + 20 - (20) = -20 - (20) -2x = - 40 divide both sides by -2 (-2x)/-2 = (-40)/-2 x = 20 Melvinas age is 20 and Bettinas age is 60