a)$.....\Rightarrow x=2\tfrac{3}{4} : (\frac{1}{2})^{3}=\frac{11}{4}:\frac{1}{8}=\frac{11}{4}.8=22 $b)$.....\Rightarrow \begin{cases}\frac{1}{2}x-1=1 \\ \frac{1}{2}x-1=-1 \end{cases}\Rightarrow \begin{cases}\frac{1}{2}x=2 \\ \frac{1}{2}x=0 \end{cases}\Rightarrow \begin{cases}x=4 \\ x=0 \end{cases}$
$\left\{ \begin{array}{l} \\ \end{array} \right.$ là $[$ nha
c)$.....\Rightarrow \frac{2x}{25}+\frac{1}{4}=\frac{3}{4}\Rightarrow \frac{2}{25}x=\frac{2}{4}\Rightarrow x=\frac{2}{4}.\frac{25}{2}=\frac{25}{4}$