13x7=!?28?!

Can thirteen times seven really equal twenty-eight???
Yes. It Can;
And no, this is NOT hobo math.
The answer is completely logical.
It is as follows:
You write 13, 7 times:

13
13
13
13
13
13
13

Add the 3s and they equal 21.Then set the 2 aside. You will use it later. Now, add the 1s. they equal 7. Put the 2 and the 8 ( include the 1 from 21)side by side, and what is it?


28.

13x7=28.