How to add spaces in calculation widget?

I used your example and for some reason i am not able to add spaces in the calculator like the example you sent me if i add spaces and add the field the spaces become brown boxes (strings) and it still not working this is your example 

and this is my example

I really hope the space is the problem i would appreciate if you can teach me how to add a space or if you see a mistake in my example please assist me i would really appreciate the help.

Thank you... Robert

Please try removing the last "+" sign and " ( ".

So that the Calculation will work correctly.

Please let us know if it doesn't work .