We have to find the distance between F=(1, -3) and G=(2, -3).
The expression for the distance of points P1=(x1, y1) and P2=(x2,y2) is:

Then, if we replace with the coordinates of F and G, we have:

The distance between F and G is 1 unit.
You can see it graphically as there is only one unit of difference in the x-axis and 0 units of difference in the y-axis.