Multiply 2 fields in a query from different tables

[Przemo]

Is it possible to multiply 2 fields from different tables in one query? It works fine when both fields are from one table, but fails when I try to use 2 different tables.I could probably do it with macro in the form that will be using that query, but that looks like an overkill…
Fedora 34, LO 7.2.6.2 Firebird
The error:

Edit: both fields were numeric. I changed them to float and it all works now! I need to read what numeric type is…

[Villeroy]

Which data type is hours.hours? It should be integer or decimal in order to be multiplyable with another number.

[Przemo]

Thank you! Having numeric type was my problem