On October 1, the company received 6 months' rent in advance from a tenant whose rent is $700 per month. The $4,200 was credited to the unearned rent acct. Record the adjustment necessary to recognize three month's rent.

If anyone is out there is this right? I posted Rent expense 2100 and unearned rent 2100. Wasn't sure if posting was to unearned rent or prepaid rent

Debit Unearned Rent Revenue for 2,100
Credit Rent Revenue for 2,100

You received rent from a tenant, which is revenue to you. If you had paid for rent then it would have been rent expense.