\ ( 72 - 18 ) ÷ 12 \ is equal to = ?

Answer: Option D

$$\begin{array}{rl}& \text{According to the question,}\\ & \frac{\sqrt{72}-\sqrt{18}}{\sqrt{12}}\\ & \Rightarrow \sqrt{\frac{72}{12}}-\sqrt{\frac{18}{12}}\\ & \Rightarrow \sqrt{6}-\sqrt{\frac{6}{4}}\\ & \Rightarrow \frac{\sqrt{6}}{2}\end{array}$$