Answer:
The journal entry for the following would be as follows:
Step-by-step explanation:
September 12 Cash A/c.................................................Dr $6,762
 Sales discount A/c..............................Dr $138
 To Accounts Receivable A/c.........Cr $6,900
As company received the cash against the sale of merchandise, asset is increasing and increase in asset will be debited. Therefore, the cash account is debited. And payment is made within the time period so discount of 2% is allowed, therefore, it is debited. And the accounts receivable account is credited with whole amount.
 Cash A/c..........................................Dr $6,900
 To Accounts Receivable A/c.........Cr $6,900
 Cash A/c..........................................Dr $5,100
 To Accounts Receivable A/c.........Cr $5,100
As company received the cash against the sale of merchandise, asset is increasing and increase in asset will be debited. And the accounts receivable account is credited. 
Working Note:
= $6,900 × 2%
= $138