For the limit approaching 3 from the right, you want to follow the line to the right of x = 3. From the graph you're describing it sounds like that's y = -3.
your answer would be 19 inches because 24 divided by 12(length of a foot in inches) is 2 and therefore you also divide 4.75 by 2 to get 2.375 and multiply that by 8 the amount of feet and your done