Intermediate Algebra/Writing Linear Equations

Linear equations have two variables: and .






If one were doing a walkathon and wanted to raise $5 for every mile walked, an equation for the total money raised,   as a function of the number of miles walked,   would be  . Would donors, however, promise to not only pay $5 per mile but give an additional $30 just for taking part, the equation would be  . 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.