To find the slant height we must take apart the pyramid first. Let us cut it in half. There we can easily see that the slant height is really just the hypotenuse of the triangle formed by half the base and the altitude.
Since the slope of the line is (31/4 - 25/4) / (5/4 - 3/4) = 3 that means that for every 1 that x increases, y increases by 3 so an example could be 1 3/4 for x and 9 1/4 for y.
