Đáp án:
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Bài `5.`
`a,`
`x+1/12=(-3)/8`
`⇔ x = (-3)/8 - 1/12`
`⇔ x = (-9)/24 - 2/24`
`⇔ x = (-11)/24`
Vậy `x=(-11)/24`
`b,`
`x-2=(-5)/9`
`⇔x=(-5)/9+2`
`⇔x=(-5)/9 + 18/9`
`⇔ x=13/9`
Vậy `x=13/9`
`c,`
`2/15 - x=(-3)/10`
`⇔ x = 2/15 + 3/10`
`⇔ x = 4/30 + 9/30`
`⇔ x = 13/30`
Vậy `x=13/30`
`d,`
`-x + 4/5 = 1/2`
`⇔ -x = 1/2 - 4/5`
`⇔ -x = 5/10 - 8/10`
`⇔ -x =(-3)/10`
`⇔x=3/10`
Vậy `x=3/10`
Bài `6.`
`x - 5/12 = 3/8`
`⇔ x = 3/8 + 5/12`
`⇔ x = 9/24 + 10/24`
`⇔x=19/24`
`223/669 - y = 11/88`
`⇔ 1/3 - y = 1/8`
`⇔ y = 1/3 - 1/8`
`⇔ y = 8/24 - 3/24`
`⇔ y = 5/24`
Có : `x + y `
`= 19/24 + 5/24`
`= 1`
Vậy `x+y=1`
Bài `7.`
`a,`
`x + 1/3 = 2/5 - (-1/3)`
`⇔ x + 1/3 = 6/15 + 5/15`
`⇔ x+1/3 = 11/15`
`⇔x=11/15 - 1/3`
`⇔x=11/15 - 5/15`
`⇔x=2/5`
Vậy `x=2/5`
`b,`
`3/7 - x = 1/4 - (-3/5)`
`⇔ 3/7 - x = 5/20 + 12/20`
`⇔ 3/7 - x = 17/20`
`⇔ x = 3/7 - 17/20`
`⇔x=60/140 - 119/140`
`⇔x=(-59)/140`
Vậy `x=(-59)/140`
