Giải thích các bước giải:
`a)`
`237-(-63) +17-60+(-40)`
`=237+63+17-60-40`
`=63-60-40+17+237`
`=(63-60)-(40-17)+237`
`=3-23+237`
`=-20+237`
`=217`
`b)`
`(3x-15)-(5x-9) =2`
`=>3x-15-5x+9=2`
`=>3x-5x-15+9=2`
`=>x.(3-5)-(15-9)=2`
`=>x.(-2)-6=2`
`=>x.(-2)=2+6`
`=>x.(-2)=8`
`=>x=8:(-2)`
`=>x=-4`