The expression provided in the image is:

$\frac{15}{\sqrt{5}} - \sqrt{20}$

Let's simplify this expression step by step.

Step 1: Simplify $\frac{15}{\sqrt{5}}$

We rationalize the denominator by multiplying both the numerator and denominator by $\sqrt{5}$:

$\frac{15}{\sqrt{5}} \times \frac{\sqrt{5}}{\sqrt{5}} = \frac{15\sqrt{5}}{5} = 3\sqrt{5}$

Step 2: Simplify $\sqrt{20}$

The square root of 20 can be broken down as:

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

Step 3: Combine the terms

Now, substitute the simplified terms:

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

Final Answer:

The simplified expression is:

$\boxed{\sqrt{5}}$

Would you like further clarification on any steps? Feel free to ask!

Here are 5 related questions to deepen your understanding:

1. How do you rationalize a denominator with a square root?
2. Why does $\sqrt{20}$ simplify to $2\sqrt{5}$?
3. How do you add and subtract radical expressions like $3\sqrt{5} - 2\sqrt{5}$?
4. What are other ways to simplify square roots of larger numbers?
5. Can all radical expressions be simplified in a similar way?

Tip: Always look for perfect square factors when simplifying square roots, as it makes the process easier.