The difference between 30 and 30 is: 
The difference between 21 and 13 is: 
The difference between 35 and 30 is: 
The difference between 30 and 30 is: 
The difference between 50 and 30 is: 
The difference between 30 and 20 is: 
The difference between 38 and 39 is: 
The difference between 30 and 30 is: 