Answer:
For the services to customers you will have Accounts Receivable (debit) for 20,000 and Sales (credit) for 20,000.
For the cash received you will have Cash (debit) for 20,000 and Accounts Receivable (credit) for 20,000.
For the advertising that is not pay yet you will have Expenses in advertising (debit) got 1,800 and Accounts Payable (credit) 1,800.
For the dividends you will have Dividends (debit) for 3,000 and Cash (credit) for 3,000 for the payment.