Frowning takes 68 muscles.
Smiling takes 6.
Pulling this trigger takes 2.
I'm lazy.
It’s called finding the “digital root”. If you multiply by 9, then the resultant number will be divisible by 9. Or, equivalently, the digital root will be 9.
If you don’t find that sort of thing fascinating by high school or earlier, you’ll probably won’t be a math major. If not, maybe physicist or engineer.