Introduced DS5 to the concept of algebra using the idea of a "mystery number" then he'd work out the problems using his balance scale. He got it right away.

(Being more humble--it's not like he's close to doing a whole lot of algebra. He doesn't know the math facts, but I've seen a few things saying that kids who don't know the math facts sometimes find interest in the higher-level areas, so I thought I'd throw it out there and give it a try. But using the balance really made the idea of balancing the sides of the equation make sense.)

This led me to apparently hit the "unacceptable level of bragging", because when I posted pics on Facebook, I only got 7 likes, and I usually get well over 20 likes for something cute or smart my kids do (recent examples being a "pretending to be a rock star" story and "Reading 'Afghanistan' in Japanese" brag).