Answer:
[tex]x+3=\sqrt{13}[/tex]
Step-by-step explanation:
For a radical equation, the unknown or the variable is located under the radical sign.
In this case our variable is x.
From the given options, [tex]\sqrt{x}+3=13[/tex] is the only radical equation.
The last equation, [tex]x+3=\sqrt{13}[/tex] is not a radical equation because the number (13) under the radical sign is constant.
The 3rd choice is correct