It's a square root addition/subtraction but I don't know how to place the symbol for the square root i.e [ math ],

so I'll try my best to describe it.

square root of plus 6 square root of minus 4 square root of

Ok here is what I did;

I subtracted + 6 square root of and -4 square root of

Then I squared off and got 12 square root of to which I added to the first square root. and I got with 12 square root of

Now the answer on the answer key is 13x square root of 3. I know I am wrong but I don't know where I am wrong.

Does squaring off the give me 3 and the x on the outside?

and what about the 13!?