1. How to calculate ending inventory if only given is beginning and purchases?
2. how to calculate working capital of Accounts receivable & re payments?

1. You can't.
2. Working capital is current assets minus current liabilities, so it doesn't just involve receivables, and "payments" is a transaction, not a balance. If you make a payment you're reducing cash, but that's affecting the balance of cash, which is not the same as the balance itself. And working capital involves more accounts than just these.