(√20-√5) *√5

To simplify the expression \((\sqrt{20} - \sqrt{5}) \cdot \sqrt{5}\), we can distribute \(\sqrt{5}\) to each term inside the parentheses:

\[ (\sqrt{20} - \sqrt{5}) \cdot \sqrt{5} = \sqrt{20} \cdot \sqrt{5} - \sqrt{5} \cdot \sqrt{5} \]

Now, simplify each term:

1. \(\sqrt{20} \cdot \sqrt{5} = \sqrt{20 \cdot 5} = \sqrt{100} = 10\)
2. \(\sqrt{5} \cdot \sqrt{5} = \sqrt{5^2} = 5\)

Putting it all together, we have:

\[ 10 - 5 = 5 \]

So, the simplified result of \((\sqrt{20} - \sqrt{5}) \cdot \sqrt{5}\) is \(5\).