Q: How much is 91 minus 66? A: 
Q: How much is 60 minus 21? A: 
Q: How much is 99 minus 66? A: 
Q: How much is 91 minus 60? A: 
Q: How much is 81 minus 66? A: 
Q: How much is 91 minus 36? A: 
Q: How much is 99 minus 64? A: 
Q: How much is 91 minus 66? A: 