I got this question. How does this game work? Really, this is one of those silly things that gets forwarded a lot. It is called Regifting Robin. The basic idea is:

- pick a 2 digit number, like 37
- subtract both the number in the tens place and the number in the ones place from the original number
- find the number you have left on a grid of “gifts” and robin will guess what your gift was

You may have seen stuff like this before and figured it out. It really isn’t too bad as long as you know two things (one is a trick)

- In a two digit number, like 37, the number is really 3*10 + 7*1. I know you may be saying “duh”, but a lot of people gloss over this little detail.
- In the gift squares, there are 100 options. Some of these are repeated.

So, let me represent this two-digit number as *ab*. This is:

And now to subtract *a* and *b* from *ab*:

There are not an infinite answers since the one’s digit cancel. There are only ten answers that you could end up with. Carefully look at the gifts you have to choose from. Here is my super-enhanced version:

Notice in this case that all the multiples of 9 have the same ‘happy face mug’ gift. Done. No magic required.

Maybe I shouldn’t give away their little trick. Well, in this case it was way too easy. Maybe this will encourage them to come up with more elaborate tricks.