Intermediate Algebra/Writing Linear Equations

Linear equations have two variables: $x$ and $y$.

Examples

$y=5+7x$

$y=2-4x+4$

$y=7/2-4x$

If one were doing a walkathon and wanted to raise $5 for every mile walked, an equation for the total money raised, $y$ as a function of the number of miles walked, $x$ would be $y=5x$. Would donors, however, promise to not only pay $5 per mile but give an additional $30 just for taking part, the equation would be $y=5x+30$. Note that this example is limited as negative miles don't make sense, but the line defined by the equation is infinite in either direction.