Let x be the drop of water level in the left tube and y be the rise of water level in the right tube,
x A1 = y A2 [bcoz volume dispace will be same]
x (2.5) = y (5) , we get x = 2y
So, equate the pressure at horizontal line passing thru B , we get the ans
Similarily for case 2,
2x' = y'
sry for the rough figure