55X8二44o,7x3=21,9十5X2=19,1ooX6十78二678,(72十8)X4÷8=40,54÷9十3X|2=42,18X2÷9=4,60ⅹ2o=1200,7oX9=63,1o0÷5X6=12o,3X4X6=72,6X6十5=41