just write out all possible pairs where the first element is greater than the second

so the relation is: R = {(4,3), (4,2), (4,1), (3,2), (3,1), (2,1)}

for the inverse relation, just switch the first and second element in each pair of the original relation

i can't help you with the directed graph, never learnt about that (i would think you just plot the points on the xy-plane and connect them with straight lines, but it might not be that intuitive)