jmc

We square both sides to get rid of the square root sign. This gives us $5+2z=121$. Solving for $z$ gives $z=\boxed{58}$. We squared an equation, so we have to test our solution to make sure it isn't extraneous. We have $$\sqrt{5+2\cdot 58}=\sqrt{121}=11$$so our solution is valid...