The problem asks us to simplify the expression $\frac{3}{\sqrt{7}}$ by rationalizing the denominator. This means we need to eliminate the square root from the denominator.

1. Problem Description

The problem asks us to simplify the expression $\frac{3}{\sqrt{7}}$ by rationalizing the denominator. This means we need to eliminate the square root from the denominator.

2. Solution Steps

To rationalize the denominator, we multiply both the numerator and the denominator by $\sqrt{7}$.

$\frac{3}{\sqrt{7}} = \frac{3}{\sqrt{7}} \cdot \frac{\sqrt{7}}{\sqrt{7}}$

$\frac{\sqrt{a}}{\sqrt{a}} = 1$

$\frac{3}{\sqrt{7}} \cdot \frac{\sqrt{7}}{\sqrt{7}} = \frac{3\sqrt{7}}{\sqrt{7} \cdot \sqrt{7}}$

$\sqrt{a} \cdot \sqrt{a} = a$

$\frac{3\sqrt{7}}{\sqrt{7} \cdot \sqrt{7}} = \frac{3\sqrt{7}}{7}$

3. Final Answer

$\frac{3\sqrt{7}}{7}$