Hi @jestes ,
That is from the cash flow statement. In it, they are counting the money which has left their accounts as the positive number, sort of the inverse of the balance sheet is calculating them. Take a look at the balance sheet and see how it relates to these values!
The cash flow statement is taking the 15,000 operating profit as a starting point. It is showing the 30,000 accounts receivable (money owed to the firm, but not yet paid) as a negative number because it is flowing into the firm. Accounts payable (money the firm owes) is positive in this case because it is money flowing from the firm. Same as the depreciation.
So, you take:
15,000-30,000+16,000+5,000 = 6,000 cashflow
The total amount of cash leaving the firm is $6,000.
You can read more about cash flow statements here:
Honestly, for some of these financing concepts websites like Investopedia can be more easily understood than other, architecture specific sources in my opinion!