This is Regifting Robin. I was introduced to her today in my email. She resides here and she has a little game for you to play.
I must warn you that she may drive you slightly batty. If you are like me, you will play again and again, all the while trying to outwit her.
But you can't. It is impossible. She WILL prevail each and every time. (Unless of course, you can't subtract a single digit from a double digit accurately. Then you are just dumb, like me, who swore I had prevailed. That is until I realized that 16 - 7 does NOT equal 8.)
So, I stopped trying to win (and do basic math) and took a look at the whole picture. I figured out the trick. It's quite simple actually.
Can you see it?