I know there are many similar questions but have not been able to find a syntax in the posts that work.

I calculate var1 and var2 in a previous portion of the script. Then i want to set var3 to var2-var1.
Have tried all kinds of variations on:

var3 = `"expr $var2 - $var1`

I'm unfortunately not exactly a unix newbie, just not a natural

thanks for any help.

-dharol