The difference between 39 and 15 is: 
The difference between 81 and 69 is: 
The difference between 36 and 15 is: 
The difference between 39 and 13 is: 
The difference between 99 and 15 is: 
The difference between 39 and 15 is: 
The difference between 40 and 16 is: 
The difference between 39 and 15 is: 