Algebra Lesson for 7th Graders

I spend an inordinate amount of time thinking about what I'm going to teach and how I'm going to teach it. I came up with this lesson this morning--having fallen asleep worrying about how and what I'm teaching next week.

You have two children, one boy and one girl.
Whatever you give to the girl you have to give to the boy, and vice versa. They ar really loud and annoying, so you have to keep everything equal.

Bank Account Game:
Materials: Slateboards/Whiteboards, pens, erasers
Setup: Draw a girl in one top corner of the board and a boy in the opposite top corner. You're going to set up a bank account for the children. Your goal is to see if you can keep both sides equal.

Rules: Start with a solved expression (like x=2)
Student calls out an action and a number from -5 to 10
You can + or - a variable
You can + - x or ÷ by a constant
and we all do it. For example "Add 2x" or "multiply by 5"
X is just a fixed amount of money in a bundle. (Different banks use different ways of bundling their money. You're new at this bank and they didn't tell you).

I would do one example round, then one class round, using a different letter as the variable each round.

Then ask how we can get back to the original solved equation. You can follow the same steps backwards (using inverse operations) to get it solved...kind of like a rubik's cube.

One day, to keep them busy, you give one of the children 3 bags of comic books and 12 more, and the other you give two bags of comic books and 16 more. And they start to complain, until you say "I gave you EXACTLY the same amount, but I'm keeping them now until you can tell me how many is in one of the bags. Each bag has the same amount in it."

At this point the class would solve the problem together.
Then I'd set the kids on 5 problems for guided practice, making sure to throw in a negative number or two, and go over it 10 minutes later.

The independent practice would be a homework assignment posted on the board.

Finally, we'd review the guided practice and I'd ask for some feedback about understanding--this tends to be a slip of paper with a checklist and room at the bottom for comments from the students.