Canyon co pays weekly salaries of 12,000 on Friday for a five day week ending on that day. What is the adjustment at the end of the accounting period?

First you need to calculate the salaries for a daily basis then take this amount times the number of days to get the adjustment amount.

For example the end of an accounting period is on a Wednesday you would take $12,000/5 = $2,400 * 3 days = $7,200
Your journal entry will be: Debit Salaries Expense 7,200 and Credit Salaries Payable 7,200

When you pay the pay the salaries on Friday your journal entry will be:
Debit Salaries Expense 4,800 (for Thursday & Friday)
Debit Salaries Payable 7,200 and Credit Cash for 12,000