长80米，宽40米。设操场的长为x米，宽为y米。xy = (x-5)(y) + 200xy = x(y+4) -320xy = xy - 5y + 200xy = xy + 4x - 320从第一个式子：xy - xy = -5y + 200=> 5y = 200; y = 40从第二个式子：xy - xy = 4x - 320=> 4x = 320; x = 80
