If $1,700 was received in January for services performed in January, what was the balance in Unearned Revenue at December 31, 2013?

Unearned Revenue 1,300
Service Revenue 3,100

My attempted answer dec31bal+3100-1700=1300 dec31bal=100 which is wrong please help by explaining thanks!

The balance in Unearned Revenue would not change because $1,700 was received in the month that the service was preformed. The service being preformed would have been a journal entry to Service Revenue not Unearned Service Revenue.