有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9

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有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9有简便法计算,20+19-18-17

有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9
有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9

有简便法计算,20+19-18-17+16+15-14-13+12+11-10-9
(20–10)+(19+11)+(18+12)(17+13)+(16+14)+(15-14)–9
=10+30+30+30+30+1–9
=10+120+1–9
=131-9
=122