The following multiple-choice is solved. Could you please explain to me why these are the results? I tried to calculate the first one, as an example but did not get the results until I did random operations that although gave the answers, I know are wrong. Could you please help me to state why these are correct? Thanks

15. Adjustments for previously recorded prepaid expenses A) Decrease assets and increase revenues B) Decrease expenses and increase assets C) Decrease assets and increase expenses D) Increase expenses and increase owner's equity E) Increase revenues and Decrease assets. 16. A company makes a credit sale of $750 on June 1, term 2/10 net 30. What amount was received in payment if the customer pays on June 9. A) 750 B) 735 C) 720 D) 740 E) 780 17. If a company uses LIFO, which of the following would most explain a decrease in the gross profit margin or rate? (assuming Revenue remains constant) A) An increase in advertising expense B) A decrease in manufacturing costs C) An increase in competition D) Purchases of inventory at the end of the period E) All of the above would decrease Gross Profit