Let's assume that you stared at the origin. So your friend moved 16 units along the x-axis and 12 down the y-axis landing him at (16, -12), while you on the other hand run 12 feet forward along the x-axis, and 9 units into the negative y area. This makes you at (-12, -9). So solve graph these points. Use the graph to count the difference between the 2 x coordinates, you should get 28, the solution for the y distance (ignore the negatives) is 3. So we can use the Palagorien Theorem to solve. (28)2 + (3)2 = x2. Solve for x.
784+9=x2
793=x2
28.1602556807=x