Originally Posted by

**Annatala** I'm so sorry. I got this backwards, just like I warned you about. :P You are building the thing you reduce from, not the other way around. I was making an error when I said "reduce to the halting problem" in another post.

The other way is impossible, which is how I figured this out. This way is doable. You have a solver for "do these trees give the same result", and you want to build a solver for "do these sequences of addition, subtraction, and multiplication give the same result". To do this, you need to turn each sequence into a tree.

I'll respond more later, can't finish this now.