repeated square roots

Let the entire thing be equal to x. Then,

 

$\sqrt{3 + x} = x$

 

$3 + x = x^2$

 

Use the quadratic formula to solve for x.

let x = your entire question

 

x^2 = 3  + sqrt 3 sqrt......

 

then x ^2  - x   = 3

x^2 -x-3   = 0                      then as Penguin said...use quadratic formula to find x  ( the positive value)