55×99=5445
555×999=554445
×=
(100﹣12)÷8=11
(1000﹣112)÷8=111
(10000﹣1112)÷8=
①15.28﹣3.6﹣3.4
②()×7.2
③
④7.5÷[(6.8﹣4.3)×0.12]