Answer:
1. Cash                                                          Debit    $ 47,000
  Accumulated Depreciation equipment   Debit  $ 40,800
  Gain on sale of equipment                       Credit                       $  11,000
  Equipment                                                  Credit                      $ 76,800
To record sale of equipment for $ 47,000 and gain on sale of $ 11,000
2. Cash                                                          Debit    $ 36,000
   Accumulated Depreciation equipment   Debit   $ 40,800
   Equipment                                                 Credit                          $ 76,800
To record sale of equipment for $ 36,000
3.  Cash                                                          Debit    $ 31,000
   Accumulated Depreciation equipment   Debit    $ 40,800
   Loss on sale of equipment                       Debit    $   5,000
   Equipment                                                  Credit                          $ 76,800                        
To record sale of equipment for $ 31,000 and loss on sale of $ 5,000
Explanation:
Computation of net book value
Cost of equipment                                                                             $ 76,800
Less: Accumulated depreciation                                                     $ 40,800
Net book value                                                                                  $ 36,000      
In first step where the equipment is sold of $ 47,000, the differential between the sale value and the net book value is the gain on sale and is credited in the accounting entry.
In the second step, where the equipment is sold for $ 36,000, the sale proceeds is exactly equal to the net book value and no gain or loss is recorded.
In the third step, the equipment is sold for $ 31,000 and the differential  between the net book value and the sale proceeds is a loss and recorded as a debit in the accounting entry