I have found a Dr. Seuss book that demonstrates the idea of linear equations. I started the lesson by reading the book to the students and creating linear equations to follow the storyline. Then we created our own, following a model I put together.
By downloading this file, you will get the Dr. Seuss book title, the lesson plan I followed, the notes I gave to the students, the examples I showed them, and a few examples that my own students made.
It took me a few months to find this book, but it demonstrates linear equations (using y=mx+b) perfectly! The students might be a bit shocked to find out they are about to read a children's story, but they will enjoy it. Who doesn't like being read to? :)