Fiona is working through the Miquon Blue book and was thrilled to hear that the pages which assign letters to numbers and manipulate them in code were exercising her pre-algebraic skills. She has older siblings whom she knows are doing algebra, and she thinks algebra must be pretty cool. I explained to her that algebra was a process of trying to figure out what a mystery number was in balanced equations. I said I was pretty sure that she'd be able to do some simple algebra if she wanted to. She was keen, so I got some wooden checkers, the pan balance and a piece of toilet paper labelled 'x'. We had great fun hiding unknown numbers of checkers under the toilet paper, setting up a balanced 'equation', and using our math skills to solve the mystery.
My other kids weren't intrigued by algebra this young, but Fiona seems to be -- likely because she's drawn magnetically to whatever the other kids are doing. Her eyes really lit up with this play. If she keeps asking and expressing an interest, she might be a candidate for Borenson's Hands-On Equations which I once looked over and really liked. We have an obscure manipulative-based program intended for high schoolers (Alge-Tiles) which I've used a bit with the older kids, but it gets into exponents and negative numbers right near the beginning. Borenson's program would be much more at Fiona's level and I've always wished for an excuse to purchase it.