Answer:
a. Journal entry to record music lesson
Date         Account title and Explanation     Debit     Credit
October   Cash                                              $12,500
                        Service revenue                                    $12,500
                 (To record music lesson for cash)
b. Journal entry to record prepaid insurance purchase
Date         Account title and Explanation     Debit     Credit
October   Prepaid insurance                         $3,660 
                        Cash                                                        $3,660 
                  (To record  prepaid insurance paid for next year)
c. Journal entry to record musical equipment purchased
Date         Account title and Explanation     Debit     Credit
October    Equipment                                    $15,500
                         Cash                                                      $15,500
                   (To record musical equipment purchase for cash)
d. Journal entry to record 
Date         Account title and Explanation     Debit     Credit
October    Cash                                              $21,000
                         Notes payable                                       $21,000
                   (To record loan taken by signing a note)