简便计算为6.3-6.3*0.6-0.4=6.3*(1-0.6)-0.4=6.3*0.4-0.4=0.4*(6.3-1)=0.4*5.3=2.12
6.3-6.3×0.6-0.4=6.3×(1-0.6)-0.4=6.3×0.4-0.4=0.4×(6.3-1)=0.4×5.3=2.12
6.3-6.3×0.6-0.4=6.3×(1-0.6)-0.4=6.3×0.4-0.4=2.12