4/5×6.7+4.3×0.8-80%7/9÷5+7/9÷239.5×10又7/8-(40-1/2)×7/81.25×25×323/8×5/7+5/8×4/7(1/2+1/4+1/8+1/16)×16（1/2-1/3+1/4)×3×40.25×3×4123×321642/1232461/4×3.58+1/4×7.42-0.25