We know that if X>Y, making Y in the downward direction positive, then the ball clears the first step, but the same is true for the remaining steps. The point at which X=Y will tell us which step the ball landed on. X=vt and Y=1/2*a*t^2. You now need to solve for t. Knowing t will then give you...
Remember that as the ball rolls off the edge the horizontal and vertical components of motion are independent of each other. The next question for you to solve then is this: In the time it will take the ball to fall 20.3 cm, how far will it have traveled in the horizontal direction at 1.52 m/s...