解:∵70%x+8=80%-100.7x+8+10=0.8-10+100.7x+18=0.80.7x=0.8-180.7x=-17.2x=-17.2/0.7∴x≈-24.57
两边同乘100:1000+(X-10)70=80X1000+70x-700=80x-10x=-300x=30