Question

Paula has a mathematical magic trick. She gives the following instructions to her friend Jessica:
-think of a number
- triple it
- add 6
- divide by 3
- add 5
- subtract your original number
Paula now knows the number Jessica ended up with.
1.) what number will the sequence of operations always lead to?
2.) Prove that the sequence always leads to this number

Answer 1

-think of a number ----- x
- triple it -------------- 3x
- add 6 ---------------3x+6
- divide by 3 ---------x+2
- add 5 -------------- x+7
- subtract your original number -------- 7
Paula now knows the number Jessica ended up with.

always 7 !