A man noticed that a tank is half full. After emptying 600 liters from the tank, he observes that it is now one-third full. How much does the tank...

The tank went from 1/2 full to 1/3 full.  Finding that difference:

1/2 - 1/3 = 1/6

So, the man emptied out 1/6 of the tank, or `x/6` where`x` is the amount of a full tank. It follows that:

`x/6  = 600`

x = 3600 L 

So, the tank holds 3600 L when full.