Answer:
General Journal 
Perpetual Inventory system
Date Particulars Debit Credit
July 3 Account Receivable $3,750
 Sales $3,750
Sold merchandise on account for $3,750 terms.
 Cost of Goods Sold $ 2000
 Merchandise Inventory $2000
The cost of the goods sold was $2,000.
 July 5 Sales Returns $1,050 
 Account Receivable $1,050 
 Issued credit memo for $1,050 for merchandise returned from sale on July 3. 
 
 Merchandise Inventory $610
 Cost of Goods Sold $ 610
The cost of the merchandise returned was $610. 
July 12 Bank (cash) $2700
 Account Receivable $2700 
Received check for the amount due for sale on July 3 less return on July 5. ($3,750- $1,050 )=$2700
July 17 Cash $ 7420
 Sales $ 7420
Sold merchandise for $7,000 plus 6% sales tax to cash customers. As sales tax is added to the sales a combined entry is made . ( 6%* 7000= $ 420)
 Cost of Goods Sold $ 3830
 Merchandise Inventory $3830
The cost of the goods sold was $3,830.