Q: How much is 16 minus 13? A: 
Q: How much is 64 minus 20? A: 
Q: How much is 19 minus 13? A: 
Q: How much is 16 minus 15? A: 
Q: How much is 36 minus 13? A: 
Q: How much is 16 minus 13? A: 
Q: How much is 21 minus 18? A: 
Q: How much is 16 minus 13? A: 