Not bad, thanks!!!

Why do you think it doesn't work something more human readable like this?

#+begin_src calc
               solve([
               a = 300 m,
               b = 300 m,
               Area = a*b,
               cost = 1 (USD/m^2),
               z = Area*cost

               ], [a, b, Area, cost, z])
#+end_src

Best regards

On Sunday, 23 Oct 2022 at 14:15, Ypo wrote:

Is it possible to express in a calc block some basic operations with
variables and non-predefined units?

Why A*c won't show an arithmetic result, but ~: A c ~?

I've never managed to get calc blocks define variables.  The equations
you have typed in are "equations" in the mathematical sense, not
assignment statements.

Is it possible to work with the "$" unit?

$ means something specific in calc (cannot remember what).  I use "USD"
instead, for instance, and it works fine.

The following single line calc block does do what you want:

#+begin_src calc
  solve([a = 300 m, b = 300 m, Area = a*b, cost = 1 (USD/m^2), z = Area*cost], [a, b, Area, cost, z])
#+end_src

#+results:
: [a = 300 m, b = 300 m, Area = 90000 m^2, cost = USD / m^2, z = 90000 USD]