The trial balance of the Jason Ltd, shown below, does not balance.

Jason Ltd.

Trial Balance

31 May 2020

	Debit		Credit
Cash	$ 3,850
Accounts Receivable			$ 2,750
Prepaid Insurance	700
Equipment	12,000
Accounts Payable			4,500
Unearned Service Revenue	560
Share Capital			11,700
Service Revenue	8,690
Salaries and Wages Expense	4,200
Advertising Expense			1,100
Utilities Expense	800
	$30,800		$20,050

Your review of the ledger reveals that each account has a normal balance, so four of the accounts in the trial balance above have been listed in the wrong column. These four errors should be seen as independent of the seven errors that follow.

1. The totals of the debit sides of the Prepaid Insurance, Accounts Payable, and Utilities Expense accounts in the ledger were understated by $100 each.
2. Transposition errors were made in Accounts Receivable and Service Revenue. Based on postings made, the correct balances were $2,570 and $8,960, respectively. The balance of $2,570 did not take into account, however, the error noted in #7 below.
3. A debit posting to Salaries and Wages Expense of $200 was omitted.
4. A $1,000 cash dividend was debited to Share Capital for $1,000 and credited to Cash for $1,000.
5. A $520 purchase of supplies on account was debited to Equipment for $520 and credited to Cash for $520.
6. A cash payment of $450 for advertising was debited to Advertising Expense for $45 and credited to Cash for $45.
7. A collection from a customer for $420 was debited to Cash for $420 and credited to Accounts Payable for $420

I am confused by how to do the cash part. In the answers, it says you have to do 3850+520- (450 - 45). Could you explain why you add 520, and subtract (450 - 45) from 3850? Thank you