On July 1 2010 spahn co. Pays $18,000 to randle insurance co. For a 3-year insurance contract. Both companies have fiscal year ending December 31. Prepare the journal entry on July 1 and the adjusting entry on December 31 for randle insurance co.

Randle is receiving the money for providing insurance services.

So your journal entry to record the receipt of money will be:
Debit Cash for 18,000
Credit Unearned Insurance Revenue (or other appropriate Unearned Revenue account) for 18,000

For the adjusting entry on Dec 31 you first have to calculate the amount of unearned revenue that is earned:

The easiest way is to first get the monthly rate for insurance, which is $18,000 divided by 36 months to get your monthly rate, then take the monthly rate times 6 months (Jul, Aug, Sep, Oct, Nov, and Dec) to get the total amount of interest earned. Or you can simply take $18,000 times 6 divided by 36, or $18,000 * (6/36)

Now your adjusting entry will be:
Debit Unearned Insurance Revenue (or other appropriate Unearned Revenue account) for the total amount of interest earned
Credit Interest Revenue (or other appropriate revenue account) for the total amount of interest earned