We are asked to simplify the expression $3\sqrt{45} - \sqrt{5}$.

1. Problem Description

We are asked to simplify the expression $3\sqrt{45} - \sqrt{5}$.

2. Solution Steps

First, we simplify $\sqrt{45}$. We can write $45$ as $9 \cdot 5$. Therefore, $\sqrt{45} = \sqrt{9 \cdot 5}$.

Using the property $\sqrt{a \cdot b} = \sqrt{a} \cdot \sqrt{b}$, we have $\sqrt{9 \cdot 5} = \sqrt{9} \cdot \sqrt{5} = 3\sqrt{5}$.

So, $3\sqrt{45} = 3(3\sqrt{5}) = 9\sqrt{5}$.

Now we can substitute this back into the original expression: $3\sqrt{45} - \sqrt{5} = 9\sqrt{5} - \sqrt{5}$.

We can factor out $\sqrt{5}$ to get: $(9-1)\sqrt{5} = 8\sqrt{5}$.

3. Final Answer

$8\sqrt{5}$