Tìm x, biết: a) x + (-2/9)=-7/12 b) (-0,1) -x = -7/6 c) (-0,12) .(x - 9/10) = -1,2 d) (x - 3/5) : -1/3 = 0,4

* Hướng dẫn giải

$$\begin{gathered} a) x+\left(-\frac{2}{9}\right)=\frac{-7}{12} \\ x=\frac{-7}{12}-\left(-\frac{2}{9}\right) \\ x=\frac{-7}{12}+\frac{2}{9} \\ x=\frac{-21}{36}+\frac{8}{36} \\ x=\frac{-13}{36} \\ Vậy x=\frac{-13}{36} \end{gathered}$$

$$\begin{gathered} b) (-0,1)-x=\frac{-7}{6} \\ x=(-0,1)-\frac{-7}{6} \\ x=\frac{-1}{10}+\frac{7}{6} \\ x=\frac{-3}{30}+\frac{35}{30} \\ x=\frac{32}{30}\text{=\hspace{0.17em}\hspace{0.17em}}\frac{16}{15} \\ \text{Vậy }x=\frac{16}{15} \end{gathered}$$

$$\begin{gathered} c) (-0,12).\left(x-\frac{9}{10}\right)=-1,2 \\ (- 0,12) . (x – 0,9) = - 1,2 \\ x – 0,9 = (- 1,2) : (- 0,12) \\ x – 0,9 = 10 \\ x = 10 + 0,9 \\ x = 10,9 \\ Vậy x = 10,9. \end{gathered}$$

$$\begin{gathered} d) \left(x-\frac{3}{5}\right):\frac{-1}{3}=0,4 \\ x-\frac{3}{5}=\frac{2}{5}.\frac{-1}{3} \\ x-\frac{3}{5}=\frac{-2}{15} \\ x=\frac{-2}{15}+\frac{3}{5} \\ x=\frac{-2}{15}+\frac{9}{15} \\ x=\frac{7}{15} \\ \text{Vậy }x=\frac{7}{15} \end{gathered}$$