IB DP World Studies EE in maths and computer science or physics and computer science?Watch
Bare in mind that the World Studies EE's are marked differently and have specific features that must be incorporated for it to fit the criteria (such a localised manifestation of the issue, and a more global one etc).
Just remember, the hardest thing about the EE, is choosing the topic. Actually writing it, although time consuming and at times a little frustrating, is tolerable so long as you've chosen something that actually has enough content to write about, with enough established investigations and data etc.
Best of luck!