need help solving in SQL solution in a single .sql file

quetion 1 and 2.. please

1) Display all invoices with balance due $200 or more (after payments and credits). Return invoice number, date of invoice, and amount due. Sort by the balance due amount in descending order. 2) Display invoice ID, payment total, and invoice_due_date from the invoices table where the payment_ total is larger than 100 and invoice_due_date is earlier than Aug 15 2014. Sort by payment total in descending order