四分之一X+40%X=421/4 x+40%x=420.25x+0.4x=42 0.65x=42 x=42/0.65 x=840/131/4 x+40%x=421/4x + 2/5x=42 (5+8)/20 x=42 13x/20=42 x=42×20/13 x=840/13