Any game of cards we play, my youngest keeps score.

It's always a challenge for her to add up scores and sometimes we toss in different rules.
For example, the game rummy (which is really easy for a 8-10 year old to learn if you make sets of 3). In this game, if you win you don't get any points--but the loser gets their score multiplied by two. Now, after the first hand is played, whoever loses gets their score multiplied by two, but the player who was the winner gets the losers original amount of points deducted from their score... lol.
Lots of addition, multiplication, & subtraction happening.
And for money games...we play a lot of life and monopoly.