You can 
put this solution on YOUR website! I am a number greater than 40.  When I am halved the answer is double 12.Double 12 is 24.  So read it this way:
When I am halved the answer is 24.
The only number which when halved gives 24 is 48.
I am a number greater than 40.Indeed, 48 is greater than 40.  So 48 is the answer.
Edwin