Answer:
Book value on date of sale = Cost - Accumulated depreciation
Book value on date of sale = $30,000 - $28,500
Book value on date of sale = $1,500
Gain on disposal = Sales amount - Book value on date of sale 
Gain on disposal = $3,500 - $1,500
Gain on disposal = $2,000
                                Journal entries
Date  Account Titles                      Debit        Credit
Cash A/C                                        $3,500
Accumulated depreciation A/C    $28,500
       To fixed asset                                           $30,000
       To gain on disposal                                  $2,000.