Algebra? Algebra!

I was around Jada's age when my best friend's dad would quiz us with what I later learned was algebra: x plus y is 3, x minus y is 1, so what are x and y?  Now that she's really getting into the math games at this online site, I figured I'd introduce these same quizzes on our walks to school. 

It's taking her a little bit to figure out - the concept of an "x" and a "y" representing unknown numbers isn't something that gets discussed often among 2nd graders at recess, after all - but at this point the goal isn't that she becomes an algebra whiz as much as that she gets introduced to the notion of algebra. 

Now with calc, I'll have to brush up first.