Snow fell from 6:30 a.m. to 11:00 a.m, accumulating at a constant rate. At 8:00 a.m., the snow was 8 inches deep. By 11:00 a.m., it was 20 inches deep.
 How much snow fell each hour?
 inches
 How much snow was already on the ground at 6:30 a.m.?
 inches
 Complete the equation that describes the relationship between the depth of the snow in inches, S, and the elapsed time in hours, t.
 Write your answer using whole numbers or decimals rounded to the nearest tenth