The answer that they gave you was the right answer. One way to solve this is to graph the two points that they gave you you could draw a line through those points and since it’s a line, draw it longer than just through those two points. Consider the rise and run or in this case drop and run which is six down and 3 to the left when going from P to the midpoint, Q. Continue this Paterson from Q and go down 6 more and left 3 more arriving at point R (-7, 0)