Answer:
April 5, purchased merchandise on account terms 2/10, n/10
Dr Merchandise inventory 22,000
     Cr Accounts payable 22,000
April 6, paid freight costs
Dr Merchandise inventory 900
     Cr Cash 900
April 7, purchase equipment on account
Dr P, P & E - Equipment 26,000
     Cr Accounts receivable 26,000
April 8, returned some merchandise (April 5th purchase)
Dr Accounts payable 2,000
     Cr Merchandise inventory 2,000
April 15, paid merchandise invoice
Dr Accounts payable 20,000
     Cr Cash 19,600
     Cr Purchase discounts 400
          or
May 4, paid merchandise invoice 
Dr Accounts payable 20,000
     Cr Cash 20,000
If the company pays the invoice on April 15th, it will get a 2% discount which must be recorded as a purchase discount.