Mode are repeating numbers in a sequence therefore 23 is your mode
check the picture below.
so, when we have a line from a 90° angle running perpendicular to the opposite side, like in this case, we end up with three similar triangles, a large one containing the other two, a medium and a small one.
now, using the sides proportions as you see there, of the small and large one, we get that much.
939/10,000 the decimal place indicates the fraction. You would love the decimal over 4 spaces which is the ten thousands place so that is what you set 939 over!