Hello, everybody :]

I'm a little confused as to the solution of a radical expression. My goal is to simplify it as much as I can. Here is the expression:

The solution which I thought would be right is:

Using Mathway.com, however, it's telling me that the answer is:

I would greatly appreciate if someone could explain how I got the wrong answer so I may learn from my mistakes. :] Thank you all very much.

Colton