Pick a whole number from 1 to 10, then multiply that number by 9.
Sum the two digits from that answer and subtract 5.
Example: You picked 7. Multiply 7 by 9. The answer is 63. Add the two digits of the answer, 63, and you get 6+3 = 9. ( This sum will always be 9.) Subtract 5 from 9 and you get 4.
It does not matter what whole number you picked in that range of 1 through 10.
You will always end up with the final number of 4.