The question is worded poorly, but it looks like you have a lever in equilibrium, with a force x at a distance d from the fulcrum, and a force y at a distance L - d from the fulcrum. You already have the equilibrium formula for this situation:
xd = y(L - d)
If you know x, y, and d, you can solve for the length L.
This is an exponential function.
Without any transformations (up or down), the range is y > 0
Answer:
Answer 1 is 3712000000
answer 2 is 8.624X10^10
answer 3 is 820
answer 4 is 380
answer 9 is 9200
answer 10 is 400
answer 11 is 8832000000
answer 12 is 1.3104X10^10