Your question is Maximizing White Selection Probability. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
If you have 100 balls, 50 white and 50 black, and two urns, how would you arrange the balls in the urns to maximize the probability of selecting a white ball?