The difference between 81 and 68 is: 
The difference between 35 and 24 is: 
The difference between 89 and 68 is: 
The difference between 81 and 60 is: 
The difference between 81 and 68 is: 
The difference between 81 and 68 is: 
The difference between 87 and 64 is: 
The difference between 81 and 68 is: 