Working on a number line, students find a way to express the addition of two integers as the addition of a single integer. This site is a sequel to Number Line I: Locations and focuses on addition of integers. The Early Algebra lessons were developed as part of a research project. Each lesson in the series includes a synopsis, step-by-step procedures, and downloadable overheads and handouts. The Early Algebra lessons cover many topics in arithmetic in novel ways that lead students into algebraic thinking. (author/sw/js)