1.5*0.9x+1.4*0.9(600-x)=7741.35x+756-1.26x=7741.35x-1.26x=774-7560.09x=18x=18÷0.09x=2001.4*0.8x=x+4201.12x-x=4200.12x=420x=420÷0.12x=3500