[underundergrad]

I have trouble regarding a retro-aldol problem. I think I've grasped the majority of it but cannot find where I went wrong to get the wrong product. I've attached the question and my attempt below. I'd appreciate if someone can point out where I went wrong since I've been staring at it for hours now.

[sjb]

As per your post report, why not post your working to help others that may come this way in the future.