Algebra provides a shorthand way to look at a whole class of relationships. Many cause-and-effect relationships in everyday life, especially those involving time and money, use linear equations and graphs as models. By understanding properties of linear models, both economists and home budget makers can plan wisely.

In this chapter you will: build on your knowledge of equations by learning to graph and write linear equations. calculate rate of change. measure direct variation. learn the slope-intercept form and the Ax+By=C form of a linear equation. write equations of lines. apply lines to scatter plots. use the x-intercept. learn about the relationships between the equations of parallel and perpendicular lines.