630÷45=630÷(5×9)=630÷5÷9=126÷9=1436×56+72×22=36×56+36×2×22=36×(56+2×22)=36×100=360099×98+198=99×98+99×2=99×(98+2)=99×100=990062×36-62+62×35=62×(36-1+35)=62×70=4340