I'm trying to check my grandaughter's homework and I need to know What is the entry for recording earned revenue of $8,000 of which $3,000 is collected in cash and the balance is due the following month.

If you are "checking" someone's homework, then you should include their answers so that we may check them, since we're not here to just give answers away.

Earnings are recorded in a revenue account, regardless of whether the cash was received or not. The accrued method states that revenues are recorded when earned. If $8000 was earned, then it's recorded as revenue. The $3000 collected in cash is taken literally -- they received $3000 in cash. The balance of $5000 is due to the company because it still needs to be paid, making it a receivable.