Answer and Explanation:
a. The journal entries are shown below:
On May 10
Merchandise inventory Dr  $75,924   ($76,800 × 0.98)
          To Account payable $75,924 
(Being merchandise inventory is purchased on account)
For recording this we debited the merchandise inventory as it increased the assets and credited the account payable as it also increased the liabilities 
On May 18
Account payable Dr
         To Cash 
(Being the cash paid is recorded)
For recording this we debited the account payable as it decreased the liabilities and credited the cash as it reduced the assets 
2. On June 1 
Equipment Dr $94,800
           To cash Dr $33,600
           To 9% Note payable $61,200
(Being the equipment is purchased on cash and note payable)
For recording this we debited the equipment as it increased the assets and credited the account payable and cash as it also increased the liabilities and reduced the assets 
3. On Sep 30
Cash Dr $180,000
    Discount on note payable $20,000
                    To Note payable $200,000
(Being the interest bearing note is recorded)
For recording this we debited the cash as it increased the assets and credited the note payable as it also increased the liabilities and the difference is debited to note payable