You, an intellectual: 9+7=16
Me, with ADHD: if you take 1 from 9 and give it to 7 thats 8+8 and 8x2 is 16
Someone, usually a Teacher: NOT LIKE THAT YOU HEATHEN
This is literally how I would have done it
9 is a hungry bitch and takes one from 7, making it 10+6=16
VALID
Both of those are fully valid mathematical strategies, and together with any other ”ten-buddies” calculation (the system of which pairs in 1-9 that make 10) (and simple memorization, they make up the basics of how the brain does arithmetics in a ten base system, whether it’s telling you or not. If you use a strategy like this, it’s both really common AND really good, since it means that you more easily can back-track, analyse and verbalize your process when needed for others or as a tool in your operation!
Cheers,
A Math teacher
iirc, seven ate nine