509*603-999999:11+3982=31591
1. 509*603＝320670
2.999999:11＝999
3.3982+999＝4881
4.320670-4881＝31591
(8535-1579):4+3456=
1. 8535-1579=6956
2.6956:4=1739
3.3456+1739=5195
(12789-8845):4+26922=27908
1.12789-8845=3944
2.3944/4=986
3.26922+986=27908
