79×28-86×0.2
=(80-1)×(30-2)-(80+6)×0.2
=80×30-80×2-30+2-80×0.2-6×0.2
=2400-16-160-30+2-1.2
=2400+2-16-160-30-1.2
=(2400+2)-(16+160+30+1.2)
=2402-207.2
=2194.8
79×28-86×0.2
=(80-1)×(30-2)-(80+6)×0.2
=80×30-80×2-30+2-80×0.2-6×0.2
=2400-16-160-30+2-1.2
=2400+2-16-160-30-1.2
=(2400+2)-(16+160+30+1.2)
=2402-207.2
=2194.8