All two digit numbers in the 10's yield an answer of 9.
All two digit numbers in the 20's yield an answer of 18.
All two digit numbers in the 30's yield an answer of 27.
All two digit numbers in the 40's yield an answer of 36.
All two digit numbers in the 50's yield an answer of 45.
All two digit numbers in the 60's yield an answer of 54.
All two digit numbers in the 70's yield an answer of 63.
All two digit numbers in the 80's yield an answer of 72.
All two digit numbers in the 90's yield an answer of 81.
Each time you do it her responses for 9, 18, 27, 36, 45, 54, 63, 72 and 81 are always the same and these are the only ones you can choose. The other numbers are just camouflage as your answer can never be one of them.
Gregg
