Prove that the number of edges is at least twice the number of vertices I need to prove that


  In a simple graph $G$, if all the $n$ vertices have a degree of at least $4$, then the number of edges is at least twice the number of vertices.


I already know that $\deg(n) = 2E$.

Then for the question 
$$\deg(n) \ge 4 = 2E$$

but then I couldn't solve further.
Hint: if you add up the degrees of all the vertices, you've counted each edge twice.