Tank B has x liters of water.
Tank A has 4 times as much, so Tank A has 4x liters of water.
After 30 liters of water were transferred from Tank A to Tank B:
Tank B has x + 30 liters of water.
Tank A has 4x - 30 liters of water.
Now, Tank B has 24 more liters than Tank A.
---> Tank B = 24 + Tank A
---> x + 30 = 24 + (4x - 30)
---> x + 30 = 4x - 6
---> x + 36 = 4x
---> 36 = 3x
---> 12 = x
Starting amounts:
Tank B = 12 liters
Tank A = 4 · 12 = 48 liters
Total amount: 12 liters + 48 liters = 60 liters.