On a sheet of paper, place a point in the upper left corner. Label the point Gotham. Then, using a ruler, draw a vertical line 7 inches long. Place point at the end of the line, and label it Smallville. From that point, draw a line to the right 6 inches in length at a slight upward angle. Label that point Will. Then, draw a diagonal line from Gotham to Will. You should have a drawing similar to this one. (this site will not let me draw a triangle such as the one I described; this one is the best I can do)
7mi | \ 8mi
Each of the vertical dashes ( | ) represents 1 mile. So, the scale is 1 inch = 1 mile
Yes, Will's location can be pin pointed.