A five-year old GOT the connection between addition and subtraction

I just got this in from a customer... how PRECIOUS!

QUOTE
Lydia, who is not yet five years old, has just started the subtraction section of Math Mammoth 1A. She made an amazing discovery and wanted to tell you about it. A photo of her letter is attached, which a translation here.

"Dear Math People,
I found out
When you do a subtraction
Backwards
It's adding
Did you know about that?
Lydia"

UNQUOTE

Lydia's mom also said that she feels Lydia is going to be so amazed when the workbook points this out a few pages from now!