Thanks Carissa. I understand your concern about my dd's "strategy" not working when there is no borrowing involved. Here is what she does:

56-38 =
50-30 = 20
6-8 = -2
20-2 = 18

58-36 =
50-30 = 20
8-6 = 2
20 + 2 =22

It works. She comes up with some different ways of doing problems so just wanted to make sure it wouldn't create future problems. Thanks!

It looks like she is showing a good sign of understanding numbers and place value.

A good mathmatician is always looking for the patterns in math, and it looks like she found one!

Have a nice day!
Carissa