The difference between 90 and 51 is: 
The difference between 29 and 20 is: 
The difference between 98 and 51 is: 
The difference between 90 and 50 is: 
The difference between 90 and 51 is: 
The difference between 90 and 21 is: 
The difference between 99 and 50 is: 
The difference between 90 and 51 is: 