42.5-22.4=20.1千克20.1+20.1=40.2千克42.5-40.2=2.3千克
42.5-22.4=20.120.1x2=40.242.5-40.2=2.3
42.5-22.4等于20.1再乘2等于40.2，42.5-40.2等于203
（42.5-22.4）×2=40.242.5-40.2=2.3
