Đáp án:
Bài `1` :
`a, 5/17 + 2/3-20/12 + 7/9 +12/17`
`= 5/17 + 12/17 + 2/3 - 5/3 +7/9`
`= 17/17 - 3/3 + 7/9`
`= 1 - 1 + 7/9`
`= 7/9`
Bài `2` :
`a, |3x + 1/2| - 2/3 = 1`
`=>|3x + 1/2| = 1 + 2/3`
`=>|3x + 1/2| = 5/3`
`=>` $\left[\begin{matrix} 3x + \dfrac{1}{2} =\dfrac{5}{3}\\ 3x + \dfrac{1}{2} = \dfrac{-5}{3}\end{matrix}\right.$
`=>` $\left[\begin{matrix} 3x =\dfrac{5}{3} - \dfrac{1}{2}\\ 3x = \dfrac{-5}{3} - \dfrac{1}{2}\end{matrix}\right.$
`=>` $\left[\begin{matrix} 3x = \dfrac{7}{6}\\ 3x = \dfrac{-13}{6}\end{matrix}\right.$
`=>` $\left[\begin{matrix} x = \dfrac{7}{6} : 3\\ x = \dfrac{-13}{6} : 3\end{matrix}\right.$
`=>` $\left[\begin{matrix} x = \dfrac{7}{18}\\ x = \dfrac{-13}{8}\end{matrix}\right.$
`b, 2 2/3 : x = 1 7/9 : 0,02`
`=> 2 2/3 : x = 16/9 : 2/100`
`=> 2 2/3 : x = 800/9`
`=> x = 2 2/3 : 800/9`
`=> x = 8/3 : 800/9`
`=> x = 3/100`
