I could absolutely be wrong too, did this to the best of my ability, with the help of a calculator.

Now get the square root of that. Which is 6.60555127546

Now simply add 0.6055512755464 to 6.60556127546 to get 7.21110255093.
And that’s your answer! Feel free to ask any questions you may have, or if you need it written on paper!

I think it is 7.21110255093.

First, get 3-sqrt(13), which is -.605551275464, then square this to get 0.366692347216. Then get the square root of that, which is 0.6055512755464. Now to the other side, get 3+sqrt(13), which is 6.60555127546. Then square this, 43.6333076628.