The problem asks to simplify the expression $\sqrt{20} - \sqrt{125} + \sqrt{45}$.

1. Problem Description

The problem asks to simplify the expression $\sqrt{20} - \sqrt{125} + \sqrt{45}$.

2. Solution Steps

First, simplify each square root individually.

$\sqrt{20} = \sqrt{4 \times 5} = \sqrt{4} \times \sqrt{5} = 2\sqrt{5}$

$\sqrt{125} = \sqrt{25 \times 5} = \sqrt{25} \times \sqrt{5} = 5\sqrt{5}$

$\sqrt{45} = \sqrt{9 \times 5} = \sqrt{9} \times \sqrt{5} = 3\sqrt{5}$

Now, substitute the simplified expressions back into the original expression:

$2\sqrt{5} - 5\sqrt{5} + 3\sqrt{5}$

Combine the terms with the same radical:

$(2 - 5 + 3)\sqrt{5} = (5-5)\sqrt{5} = 0\sqrt{5} = 0$

3. Final Answer

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