Is A subset of B in this proof involving sets and integers?

[Andrax]

Homework Statement

A = { pi + 2k pi / k \in Z }
B = {(- pi / 3) + (2k pi / 3 ) / k \in A }
Prove that A C B

Homework Equations

A C B = \forallXE E : x \ni A \Rightarrow X \ni B

The Attempt at a Solution

\ni[k E Z ]: x = pi + 2k pi
\ni[k E Z ]: x = pi ( 1 + 2k)
I'm sure i need to get a k and replace it with k' to prove that it belongs to B

 

[Andrax]

Edit : solved it by replacing pi by -pi/3+4pi/3 which led to the correct answer