`7/23 + 4/17 - 7/23 + 13/17`
`= (7/23 - 7/23)+( 4/17 + 13/17)`
`= 0 + 17/17`
`= 0+ 1= 1`
`----------`
`b)` đề ko rõ
bài `2`
`a) 7/8 + x= 3/5`
`=> x= 3/5- 7/8`
`=>x=-11/40`
`b) 1/2 x - 2/5=1/5`
`=> 1/2 x = 1/5 + 2/5`
`=> 1/2 x =3/5`
`=>x= 3/5 : 1/2`
`=>x=3/5 xx 2`
`=>x= 6/5`
`c) |x+1|=2`
`TH1`
`x+1=2`
`=>x=2-1`
`=>x=1`
`TH2`
`x+1=-2`
`=>x= -2-1`
`=>x=-3`
`d)(2-x)(4/5-x)=0`
`TH1`
`2-x=0`
`=>x= 2-0`
`=>x=2`
`TH2`
`4/5-x=0`
`=>x=4/5-0`
`=>x=4/5`
`b)19 1/4 - 7/12- 15 1/4 -7/12`
`= ( 19 1/4 - 15 1/4 ) -( 7/12- 7/12)`
`= 4 -0`
`=4`