That is to find the probability that b/a is less than 2.

Take A as X and B as Y, draw a picture, make a possible combination of A and B (a rectangle), and then draw a straight line y=2x to divide the rectangle into two parts. The answer is to find that the area below is larger than the whole area.

I don't have any draft paper in my hand, and it's too brain-consuming to do oral calculations. Give me an idea, I hope it helps.