We see that that some of the points on line l are (0, 5) and (3, 0) and some of the points that are on line m are (0, 2) and (7, 0).

For line l, for every increase of 3 in the x direction, there is a decrease of 5 in the y direction. Since we want y = 15, we will increase y two times to get to (0, 15). This will cause x to decrease by 3 two times as well, so we'll get (-6, 15) for line l. For line m, we want to increase 13 units upwards, and every 2 units up causes 7 units left. Therefore, (13)(7/2) = 91/2.

Therefore, the coordinates of the point on line m is (-91/2, 15). The difference in the x-coordinates are -6-(-91/2) = 79/2