It doesn't work on the 1st problem, while it works on 2nd and 3rd problems.

Worksheet3.sm (11,41 KiB) descargado 1021 vez(es).

This is probably a bug in the expression recognition function. When trying to select a list of functions, they are not recognized correctly.

The find() function supports different forms of problem representation; you can iterate through them until the problem is solved.