Simplification of Addition of Radicals

Question

I know this may be a basic question, but I cannot seem to get the right simplification process for the following equation:

$\sqrt{36+64+5^2} + \sqrt{20}$

I do know that the correct answer is 7√5, but I cannot seem to arrive at this answer.

This is how I broke it down.

Option 1:

√105 + 2√5

Option 2:

√100 + 5 + 2√5
10 + 5 + 2√5
15 + 2√5

I appreciate feedback on where I made a mistake.

Answer 1

Note that $36+64+5^2=125,$ not $105$. Then $\sqrt{125}=5\sqrt 5$ and $\sqrt{20}=2\sqrt 5$ so the sum is $7\sqrt 5$