Here is an older riddle, if I can call it that, which your students may love.
“Take any number. Now add 5 to it. Multiply that by 2. Subtract 6. Divide by 2 and finally subtract 2 and you back to your original number. Why does this work?”
3) Have them write down the whole operation, paying special attention to order of operations. (((((x + 5) * 2) – 6) / 2) – 2)
4) Again, let them try to figure out why it works on their own.
5) Ask them to go through the following operation ((((5 * 2) – 6) / 2) – 2) and see what number they get (zero is the answer)
6) Ask them to restate the Additive Identity
7) Thus, this whole problem is simply a fancy way of adding zero to your initial number.