ข้อสอบคณิต O-NET - 2553

$$\begin{gathered} \mathrm{จากสูตร} \left|x\right| = A \\ \mathrm{จะได้} x = A, -A \\ \mathrm{จากโจทย์} 2\left|5-x\right| = 1 \\ \mathrm{จะได้} \left|5-x\right| = \frac{1}{2} \end{gathered}$$

$$\begin{gathered} 5-x = \frac{1}{2} 5-x = -\frac{1}{2} \\ 5-\frac{1}{2} = x 5+\frac{1}{2} = x \\ x = 4.5 x = 5.5 \\ \mathrm{ดังนั้น} \mathrm{ตอบ} \mathrm{ข้อ} 4 \end{gathered}$$