1.25+3.7+0.75
=(1.25+0.75)+3.7
=2+3.7
=5.7
51.27-8.66-1.37
=(51.27-1.37)-8.66
=49.9-8.66
=41.24
1.2*2.5+0.8*2.5
=(1.2+0.8)*2.5
=2*2.5
=5
(1+3)+(0.75+0.25+0.7)=4+1.7=5.7
第早搏一题先用1.25加0.75
第二题用51.27先汪态-1.37
第三陆陵祥题先用(1.2+0.8)*0.5
=1.25+0.75+3.7
=2+3.7
=5.7
这算什么问题啊