As per Your input's the Laptop accounted in FA - Rs. 20k. Sold Rs. 4k.
As per me the Entries like below :
Receipt :
Cr. Laptop A/c - Rs.4000/-
Dr. Cash A/c - Rs. 4000/-
(Give suitable Narration about the transaction)
After the receipt entry the Laptop balance shown Rs. 16000/-.
Now Provide @ 40%*** Depreciation on Laptop Entry. As per the said period depreciation to be provide above 180days as Rs. 8000/-
Journal :
Dr. Depreciation on Laptop - Rs. 8000
Cr. Laptop A/c - Rs.8000/-
(Give suitable Narration about the transaction)
After the Journal entry (depreciation) the Laptop balance shown Rs. 8000/-. Now the 8000 is loss of sale of Laptop. So, You want enter journal entry to PandL a/c.
Journal :
Dr. Loss on Sale of Laptop - Rs. 8000/- (ledger under Indirect Expenses)
Cr. Laptop A/c - Rs.8000/-
(Give suitable Narration about the transaction)
The Process is completed.
Note :
here you are not asking GST entry. So, I'm not give GST entry...