How do you rationalize the denominator 3/(sqrt3-1)?

We can multiply and divide by $\sqrt{3} + 1$ to get:
$\frac{3}{\sqrt{3} - 1} \cdot \textcolor{red}{\frac{\sqrt{3} + 1}{\sqrt{3} + 1}} =$
$\frac{3 \sqrt{3} + 3}{3 - 1} = \frac{3 \sqrt{3} + 3}{2}$