The heck, what math are you in?
I don't quite understand the ten strategy, or what EXACTLY you're asking. But, what you can do is when you add a one digit number plus a nine, just change the nine to a ten and subtract one. It is very easy. So, 7+10 equals 17, subtract one and you get 16 which is 7+9. It is always one less than anything plus 10.
