SQL Server 2012 :: How To Accumulate Additional Values To Existing Column

I have some transactions with the same card number that needs to add value amount to its existing balance. For example:

Card Number Balance Amount Issue Date Issue Branch.
4000111122223333 $100.00 10/1/2015 123 <= This is an existing row in Card Number SQL table.

Now, the same card number with additional $50 dollars that I want to add to this card number to make the total to become $150. This additional $50 is from another transaction table. On the contrary, I will have -$20 from the same card number in different transaction that I will need to deduce $150-$20 to become $130. How can I update the card number table with debit/credit transactions to keep the outstanding balance?