972÷(720-21×33) =972÷9÷(720÷9-21×33÷9)=108÷(80-77)=108÷3=36250+240÷8×5 =250+30×5=240+150=390840÷40+40×40 =21+1600=1621【175-(49+26)】×23 =【175-75】×23=100×23=2300