After t minutes, Tank A contains
6000 gal - (2 gal/min) t
while Tank B contains
8250 gal - (3 gal/min) t
The two tanks hold the same amount of water when these quantities are equal. Solve for t :
6000 gal - (2 gal/min) t = 8250 gal - (3 gal/min) t
(1 gal/min) t = 2250 gal
t = (2250 gal) / (1 gal/min) = 2250 min