Straight outta my math book...algorithm?

Question

"Cathy found her own algorithm for subtraction. She subtracted as follows:

_97

-28

-----

_-1

+70

------

_69

How would you respond if you were her teacher?"

(Ignore the underscores)

I don't know how I would respond...

...Got any suggestions?

Pleaseee

Answer 1

Your question is not clear. Could you clarify farther, what the question is!

Answer 2

I dont see any problem. If you want her to do it "your" way, tell her so ~

if i am her teacher, i will explain to her that her way is absolutely fine, but there is another way to solve this problem, and i will 'teach' her 'my' way.