Answer:
June 15, 2017, goods sold on account to Greig
Dr Accounts receivable 1,990
  Cr Sales revenue 1,990
Dr Cost of goods sold 1,310
  Cr Merchandise inventory 1,310
July 15, 2017, payment collected from Greig
Dr Cash 1,990
  Cr Accounts receivable 1,990
The transaction must be recorded only after some type of consideration is exchanged between the parties.