how to make calculation (+,-,*,/) for text in acad ????

If you mean calculation in commandline e.g., you can use this:a/b:  a/ba*b:  (* a b)a+b:  (+ a b)a-b:  (- a b)where a and b are any numbers, and spaces are necessary between sign and numbers.It's a LISP expression, probably it doesn't work in AutoCAD LT.

There are also other tools to evaluate expressions in AutoCAD - e.g. text/numbers in tables (TABLE entities), in FIELDs or in dialogs. See:
http://www.cadforum.cz/cadforum_en/qaID.asp?tip=3676
http://www.cadforum.cz/cadforum_en/qaID.asp?tip=4280