It is a question based on areal probability actually..Let us see how to do it..Consider a graph with x ranging from 0 to 3 along x axis and y ranging from 0 to 4 along y axis..
Now we need to find the favorable area in this case..
Total area = 3 * 4 = 12 sq units..
Now for favorable area we need to look into the graph..The graph looks like :
The area upon which we are interested i.e. comprising the coordinates (x,y) where x < y and x and y are real numbers hence the concept of area comes into picture..
Hence the shaded area = 1/2 * (sum of parallel edges) * perpendicular distance between them
= 1/2 * (1 + 4) * 3
= 15 / 2
Hence P(x < y) = Shaded area / Total area
= (15/2) / 12
= 15 / 24
= 5 / 8
Hence C) is the correct answer..