[fgeiger]

> It needs a lot of backtracking planning. I has to guess which will be the last expression and try to reach the numbers that it used.

I ended up creating a mental factorization table of the target number with only the available numbers as factors. That pretty "quickly" lead to a solution in only three steps.

I put the "quickly" in scare quotes because I essentially brute forced the problem.

[rntksi]

I'm pretty sure this is the only way to solve it (factorization table). I don't see how else?