Answer:
Bad debt expense $ 1,020 
Accounts Receivable $ 1,020 
Step-by-step explanation:
Initial Balance 
Accounts Receivable $ 48,400 
Allowance for Uncollectible Accounts $ 940 
 
During 2019, Coolwear wrote off $820 in accounts receivable 
Allowance for Uncollectible Accounts $ 820 
Accounts Receivable $ 820 
 
Accounts Receivable $ 47,580 
Allowance for Uncollectible Accounts $ 120 
 
Determined that there should be an allowance for uncollectible accounts of $1,140 at December 31, 2019  
Bad debt expense $ 1,020 
Accounts Receivable $ 1,020 
 
Final Balance 
Accounts Receivable $ 47,580 
Allowance for Uncollectible Accounts $ 1,140 
Accounts Uncollectible are those credit that the company give and there are not chances of been collected. 
When the customers buy products on credits but then the company can't collect the debt, then it's necessary to write off the unpaid bill as uncollectible 
 
One way it's to write-off directly the bad debts at the moment decided that the credit are uncollectible, the total amount it's reported as bad debt expenses which affect negativly the income statement and the accounts receivable are reduce in the same amount, less assets. 
 
The other way it's to determine a percentage of total amount of accounts receivables as uncollectible, exist many ways to analize the accounts receivable and figure the value of uncollectible. 
When the company have the percentage of uncollectible accounts the journal entry required is Bad Expenses (debit) with Allowance for Uncollectible Accounts (credit) 
At the moment of the write-off as the expenses were before recognized we only use the Allowance for Uncollectible Accounts (Debit) with Accounts Receivable (Credit), with this we are recognizing the uncollectible credit of the company.