At the end of a snow storm, Allison saw there was a lot of snow on her front lawn. The temperature increased and the snow began to melt at a steady rate. There was a depth
of 20 inches of snow on the lawn when the storm ended and then it started melting at
a rate of 1.25 inches per hour. Write an equation for S, in terms of t, representing the
depth of snow on Allison's lawn, in inches, t hours after the snow stopped falling.