Ta có :
\(\frac{1}{8}< \frac{x}{12}< \frac{1}{4}\)
\(\Leftrightarrow\)\(\frac{3}{24}< \frac{2x}{24}< \frac{6}{24}\)
\(\Leftrightarrow\)\(3< 2x< 6\)
\(\Leftrightarrow\)\(2x\in\left\{4;5\right\}\)
Loại \(x=5\)vì \(x\in Z\)
Do đó :
\(2x=4\Rightarrow x=\frac{4}{2}=2\)
Vậy \(x=2\)
\(\frac{1}{8}< \frac{x}{12}< \frac{1}{4}\Rightarrow\frac{1.3}{8.3}< \frac{x.2}{12.2}< \frac{1.6}{4.6}\)
\(\Rightarrow\frac{3}{24}< \frac{2x}{24}< \frac{6}{24}\)
\(\Rightarrow\frac{2x}{24}=\frac{4}{24}\)hoặc \(=\frac{5}{24}\)
mà \(\frac{2x}{24}=\frac{4}{24}\Rightarrow2x=\frac{4.24}{24}=4\Rightarrow x=\frac{4}{2}=2\)( luôn đúng)
=> x = 2 ( đpcm)
