Natural frequency of pulley system

[kyu]

Homework Statement

https://www.physicsforums.com/attachments/197474

Homework Equations

3. The Attempt at a Solution [/B]
ma + kx = 0
I know how to do it if the spring is in the middle of the pulley, not using energy method. by the free body diagram. But I am stuck at this. [Updated: I know how to solve already]

 

[zwierz]

the picture is of very bad quality