Not to be a naysayer, but there ARE techniques for single digit multiplication and addition. In fact, it’s utilizing some basic principles, like the transitive property.
You can always always breakdown mathematics into smaller bits, like 9+8=(9+1)+7=17, or 7*6=(5+2)*6=30+12=42.
You could even do counting! 1+3 => 1…2,3,4 => 4. Or 3*4 => 3,6,9,12 => 12. There’s lots of shortcuts!