`1) 4/5 - 7/6 + (-6/15)`
`=24/30 - 35/30 + (-12/30)`
`=\frac{24-35+(-12)}{30}`
`=-23/30 .`
`2)-6/9 + 7/13 + 6/13 - 5/9 + 3 7/9`
`=-6/9 + 7/13 + 6/13 - 5/9 + 34/9`
`=(-6/9 - 5/9 + 34/9) + (7/13 + 6/13) `
`=23/9 + 13/13 `
`=23/9 + 1 `
`=23/9 + 9/9 `
`=32/9.`
`3) 6 3/8-(4 3/8 - 1/2)`
`= 51/8 - (35/8 - 4/8)`
`= 51/8 - 31/8`
`= 20/8 = 5/2.`
`4) 2 1/3. 1,5-(11/10+50%):4/5`
`=7/3 . 3/2 - ( 11/10 + 1/2 ) : 4/5`
`=7/2 - ( 11/10 + 5/10 ) . 5/4 `
`= 7/2 - 16/10 . 5/4`
`= 7/2 - 8/5 . 5/4`
`= 7/2 - 2`
`= 7/2 - 4/2`
`= 3/2.`
`6) 3/2 + x = 5/3`
`⇔ x = 5/3 - 3/2`
`⇔ x = 1/6.`
Vậy ` x = 1/6 .`
`7) 5 2/3 - (3/2+x)= 4 1/3`
`⇔ 17/3 - 3/2 - x = 13/3`
`⇔ 25/6 - x = 13/3`
`⇔ x = 25/6 - 13/3`
`⇔ x = -1/6 .`
Vậy ` x = -1/6.`
`8) ( x- 1/2 )+ 75% = 9/10`
`⇔ x - 1/2 + 3/4 = 9/10`
`⇔x = 9/10 - 3/4 + 1/2`
`⇔x = 13/20 .`
Vậy ` x = 13/20.`
`9) (x-1/2)^2 - 1/9 = 0`
`⇔ (x-1/2)^2 = 0 + 1/9 `
`⇔ (x-1/2)^2 = 1/9 = (1/3)^2 = (-1/3)^2 `
`⇒` \(\left[ \begin{array}{l}x-\frac{1}{2}=\frac{1}{3}\\x-\frac{1}{2}=\frac{1}{3}\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=\frac{5}{6}\\x=\frac{1}{6}\end{array} \right.\)
Vậy `x∈{5/6 ; 1/6}.`
