You use what ever the $$ amount is that you received when you sold the partnership interest; if line 19A is what you received, then that is your selling price. However, I imagine it is some other amount based on the limited facts. You should know exactly what this amount is as you received the funds.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
