The statements of financial position of Claude company include the following

Interest receivableI don't know the procedure what I should subtract, or what I should add. For example, when I want to know cash paid for supplies, why do we subtract supplies (2019) and add supplies (2020) ? Can anyone help?

Ex. 249 The statements of financial position of Claude Company include the following: 12/31/20 12/31/19 Interest Receivable -0- Supplies 5,000 3,000A Salaries and Wages Payable 4,100 3,800 Unearned Service Revenue -0- 4,000 4,300 V The income statement for 2020 shows the following: Interest Revenue Service Revenue Supplies Expense Salaries and Wages Expense 16,400 V 75,700 10,700 A 41,000 Instructions Calculate the following for 2020: 1. Cash received for interest. 2. Cash paid for supplies. 3. Cash paid for Salaries and wages. 4. Cash received for revenue. 12.100 Solution 249 (15 min.) 1. Cash received for interest = Interest Revenue Less: Interest Receivable Cash Received 16,400 4,300 12,100 12.700 2. Cash paid for supplies = Supplies Expense Less: Supplies (2019) 10,700 3,000 7,700 5,000 12,700 Add: Supplies (2020) Cash Paid 40.700 3. Cash paid for wages = Salaries and Wages Expense Add: Salaries and Wages Payable (2019) 41,000 3,800 44,800 4,100 40,700 Less: Salaries and Wages Payable (2020) Cash Paid 71,700 4. Cash received for revenue = Service Revenue Less: Unearned Service Revenue (2020) Cash Received 75,700 4,000 71,700 LO 1, BT: AP Difficulty: Hard, TOT: 15 min., AACSB: Analytic, AICPA BB: None, AICPA FN: Reporting, AICPA PC: Problem solving