Answer
$ t (in s) = \frac{V}{v} $
Work Step by Step
Assuming the tank was empty and denoting V as the volume of the tank in L and v as the discharge rate of gasoline in L/s:
$ t(s) = V(L) \times \frac{1}{v(\frac{L}{s})} $
In units:
$ s = L \times \frac{s}{L} $
Hence the time it would take is $ t (in s) = \frac{V}{v} $
P.S. If the tank has an initial volume $V_{0}$, the time it would take is $ t (in s) = \frac{V - V_{0}}{v} $.
