(1)x+40%x=280 1.4x=280 1.4x÷1.4=280÷1.4 x=200;(2)1-20%x=0.8 1-20%x+20%x=0.8+20%x 20%x+0.8=120%x+0.8-0.8=1-0.8 20%x=0.2 20%x÷20%=0.2÷20% x=1.