Question

Mike thought of a number. He added to it two other numbers. One of these numbers was 12 less than his number, the other was 12 more than his number. The result of addition was 15. What was Mike’s original number? Answer:

Answer 1

so we have three numbers
x
x+12 (a number 12 more than our original one)
x-12 ( a number 12 less than our original one)
the sum of all these numbers was 15, thereful:
x+x+12+x-12=15
3x=15
x=5
mikes original number is 5