4/5×1/4-1/2X=1/20解:1/5-1/2X=1/201/2X=1/5-1/201/2X=3/20X=3/20÷1/2X=3/10
4/5x1/4-1/2x=1/201/5-1/2x=1/201/2x=1/5-1/201/2x=3/20x=3/20÷1/2x=3/10