The difference between 20 and 18 is: 
The difference between 52 and 23 is: 
The difference between 29 and 18 is: 
The difference between 20 and 10 is: 
The difference between 40 and 18 is: 
The difference between 20 and 18 is: 
The difference between 23 and 11 is: 
The difference between 20 and 18 is: 