0.8×100.1
=0.8×(100+0.1)
=0.8×100+0.8×0.1
=80+0.08
=80.08
(1.25-0.125)×8
=1.25×8-0.125×8
=10-1
=9
15÷0.125
=15÷1/8
=15×8
=120