0.45×(x+0.4)=0.9 0.45x+0.18=0.9 0.45x=0.9-0.18=0.72 x=0.72÷0.45=1.6 或者: x+0.4=0.9÷0.45 x+0.4=2 x=2-0.4 x=1.6
