Prove A C B for Set Theory: Help with Pi 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 = $\forallX$E 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.