In order to work this problem, I analyzed and recorded the following... I showed my work at the bottom. But I have no idea whether or not I've done this correctly. Can anyone help, please? 
AHH!
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Nov.20 Sold two items of merchandise to Cheryl Jahn, who paid the $400 sales price in cash. The goods cost Bear's $300.
Nov.25 Sold 20 items of merchandise to Vasko Athletics at a selling price of $4,000 (total); terms 3/10, n/30. The goods cost Bear's $2,500.
Nov. 28 Sold 10 identical items of merchandise to Nancy's Gym at a selling price of $6,000 (total); terms 3/10, n/30. The goods cost Bear's $4,000.
Nov. 29 Nancy's Gym returned one of the items purchased on the 28th. The item was in perfect condition, and credit was given to the customer.
Dec. 6 Nancy's Gym paid the account balance in full.
Dec. 30 Vasko Athletics paid in full for the invoice of November 25, 2010.
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This is what I did.
First, I took the $6000 and divided it by 10.
Then I did 6000-600=5400.
5400 x 3% = 162
5400-162=5238
5238-400(from Nov.20 sales price?)=4838
4838+4000(Nov.25 accts rec?)=8838
But 8838 is incorrect and I would like to know why and what I did wrong.
AHH!__________________________________________________________________
Nov.20 Sold two items of merchandise to Cheryl Jahn, who paid the $400 sales price in cash. The goods cost Bear's $300.
Nov.25 Sold 20 items of merchandise to Vasko Athletics at a selling price of $4,000 (total); terms 3/10, n/30. The goods cost Bear's $2,500.
Nov. 28 Sold 10 identical items of merchandise to Nancy's Gym at a selling price of $6,000 (total); terms 3/10, n/30. The goods cost Bear's $4,000.
Nov. 29 Nancy's Gym returned one of the items purchased on the 28th. The item was in perfect condition, and credit was given to the customer.
Dec. 6 Nancy's Gym paid the account balance in full.
Dec. 30 Vasko Athletics paid in full for the invoice of November 25, 2010.
__________________________________________________________________
This is what I did.
First, I took the $6000 and divided it by 10.
Then I did 6000-600=5400.
5400 x 3% = 162
5400-162=5238
5238-400(from Nov.20 sales price?)=4838
4838+4000(Nov.25 accts rec?)=8838
But 8838 is incorrect and I would like to know why and what I did wrong.