The difference between 81 and 64 is: 
The difference between 87 and 16 is: 
The difference between 88 and 64 is: 
The difference between 81 and 60 is: 
The difference between 91 and 64 is: 
The difference between 81 and 24 is: 
The difference between 88 and 61 is: 
The difference between 81 and 64 is: 