Tìm x, biết: a) x.14/27 = -7/9; b) (-5/9):x = 2/3; c) 2/5 : x = 1/16 : 0,125;

* Hướng dẫn giải

$$\begin{gathered} a) x\cdot \frac{14}{27}=\frac{-7}{9}; \\ x=\frac{-7}{9}:\frac{14}{27} \\ x=\frac{-7}{9}\cdot \frac{27}{14} \\ x=\frac{-3}{2} \\ Vậy x=\frac{-3}{2} \end{gathered}$$

$$\begin{gathered} b) \left(\frac{-5}{9}\right):x=\frac{2}{3} \\ x=\left(-\frac{5}{9}\right):\frac{2}{3} \\ x=\left(-\frac{5}{9}\right)\cdot \frac{3}{2} \\ x=\frac{-5}{6} \\ Vậy x=\frac{-5}{6} \end{gathered}$$

$$\begin{gathered} c) \frac{2}{5}:x=\frac{1}{16}:0,125 \\ \frac{2}{5}:x=\frac{1}{16}:\frac{125}{1000} \\ \frac{2}{5}:x=\frac{1}{16}:\frac{1}{8} \\ \frac{2}{5}:x=\frac{1}{16}\cdot 8 \\ x=\frac{2}{5}:\frac{1}{2} \\ x=\frac{2}{5}\cdot 2 \\ x=\frac{4}{5} \\ Vậy x=\frac{4}{5} \end{gathered}$$

$$\begin{gathered} d) -\frac{5}{12}x=\frac{2}{3}-\frac{1}{2}. \\ \frac{-5}{12}x=\frac{4}{6}-\frac{3}{6} \\ \frac{{\displaystyle -5}}{{\displaystyle 12}}x=\frac{{\displaystyle 1}}{{\displaystyle 6}} \\ x=\frac{{\displaystyle 1}}{{\displaystyle 6}}:\frac{{\displaystyle -5}}{{\displaystyle 12}} \\ x=\frac{{\displaystyle 1}}{{\displaystyle 6}}\cdot \frac{{\displaystyle 12}}{{\displaystyle -5}} \\ x=\frac{{\displaystyle -2}}{{\displaystyle 5}} \\ Vậy x=\frac{{\displaystyle -2}}{{\displaystyle 5}} \end{gathered}$$