Students identify independent and dependent variables and represent linear relationships with tables, graphs, and equations such as $y=kx$ and $y=mx+b$. They recognize constant first differences and constant rates of change, determine rate of change from tables or graphs as $\Delta y/\Delta x$, and distinguish linear relationships from nonlinear ones. Students plot ordered pairs, interpret points and scales in context, and distinguish proportional relationships that pass through the origin from nonproportional linear relationships with an initial value.