8.2×9.9=8.2×10-8.2×0.1=82-0.82=81.18
8.2×(10-0.1)=8.2×10-8.2×0.1=82-0.82=81.18
8.2x9.9 =8.2*(10-0.1) =8.2*10-8.2*0.1 =82-0.82 =81.18