Bài 5. (1,5 điểm). Tìm x biết: a) $x- \frac{-3}{4}$ = $\frac{1}{3}$ + $\frac{1}{6}$  b) $ x: \frac{1}{5}$ = $\frac{1}{7}$ - $\frac{1}{5}$  c) $\frac{8}{7}x$ -$\frac{3}{7}x$ = $\frac{1}{14}$ -$\frac{2}{7}$ 

Bài `5:`

`a)` `x- (-3)/4 = 1/3 + 1/6`

`=> x + 3/4 = 2/6 + 1/6`

`=> x + 3/4= 1/2`

`=> x=1/2 - 3/4`

`=> x= 2/4 - 3/4`

`=> x=-1/4`

Vậy `x=-1/4`

`b)` `x : 1/5 = 1/7 -1/5`

`=> x . 5= 5/35 - 7/35`

`=> x . 5 = -2/35`

`=> x= -2/35 : 5`

`=> x= -2/35 . 1/5`

`=> x=-2/175`

Vậy `x=-2/175`

`c)` `8/7x-3/7x=1/14-2/7`

`=>` `8/7x-3/7x=1/14 - 4/14`

`=>` `8/7x-3/7x=-3/14`

`=>` `(8/7-3/7)x=-3/14`

`=>` `5/7x=-3/14`

`=>` `x=-3/14 : 5/7`

`=>` `x=-3/14 . 7/5`

`=>` `x=-3/10`

Vậy `x=-3/10`