Family visit visa from Pakistan with 4 large credits in bank statement. How to justify?

This is really simple. You need to provide good reliable documents that back up what you say about the money transfers. For example:

• To prove that you transferred 7500 GBP from your savings accounts, provide statements from the savings accounts. This will not only confirm the transfer is what you say, but give a much better picture of your finances.
• To prove that the 16000 GBP came from sale of a property, provide documents showing that you did in fact sell a property, and it was for 16000 GBP

The transfer of 7500 GBP almost certainly hurt you because it looks like what we call 'funds parking'. You will have to work extra hard in future applications (meaning provide extremely good documentation) to overcome the suspicion that you have been doing this. The best way to do this would have been to not transfer the money out of the savings account, but just to provide statements from the savings account to show that you have the money.

Selling the property was also a bad move. Not only does it look like you were trying to inflate your funds available, owning property would have provided you with ties to your home country, and increased the likelihood that you were accepted. Selling property makes it look like you are preparing to leave the country. If time and circumstances permit, using the funds from the sale to buy the new home you are wanting would both remove the problem of the 16000GBP and give you additional ties to your home country.