Paul and his neighbors decided to build a fence along his farm. after three hours, they have 15 meters of fencing complete. they decide to take a 2-hour break for lunch and then resume building the fence. after four more hours, they have a fence that is a total of 55 meters long. construct the graph that models the given situation.

Let the  be the time in hours, and  meters of fencing completed. 
We know that After three hours, they have 15 meters of fencing complete, our graph will go from the point (0,0) to the point (3,15). We also know that they decide to take a 2-hour break for lunch and then resume building the fence, so our graph will go from the point (3,15) to the the point (5,15). Finally, After four more hours, they have a fence that is a total of 55 meters long, so the final part of our graph will go from the point (5,15) to the point (9,55)

We can conclude that the graph of t vs y is: 

You want to isolate your variable.