3
  x
 x
x    = 3

I agree that right-to-left (upper-right to lower left) is the way, so that the spreadsheet can solve (after taking log of both sides twice) x^3*log(x) + log(log(x)) = log(log(3))

Having a cell in Excel for x^3 (as well as the other components),  and using Solver to equate the two sides, it shows that x^3 = 3.

Then it becomes obvious: when x is the cube root of 3, the top x^3 is 3; then the next one is also 3, and so on; it could actually go on for any number of levels.  At that point it is: aha! why didn't I think of that?