1. **State the problem:** Simplify the expression $$2\sqrt{5} + \sqrt{5} + \sqrt{20}$$. 2. **Recall the rules:** - Like terms with square roots can be combined if the radicands (numbers inside the root) are the same. - Simplify square roots when possible, e.g., $$\sqrt{20} = \sqrt{4 \times 5} = 2\sqrt{5}$$. 3. **Simplify each term:** - $$2\sqrt{5}$$ stays as is. - $$\sqrt{5}$$ stays as is. - $$\sqrt{20} = 2\sqrt{5}$$. 4. **Combine like terms:** $$2\sqrt{5} + \sqrt{5} + 2\sqrt{5} = (2 + 1 + 2)\sqrt{5} = 5\sqrt{5}$$. 5. **Final answer:** $$\boxed{5\sqrt{5}}$$