1 US gallon = 3.78541 liters
1 minute = 60 seconds
Remember how we can multiply anything by 1 and it doesn't change? We can multiply by (3.78541 liters / 1 gallon) because (3.78541 liters / 1 gallon) = 1. We can do this:
(8.5 gallons / 1 minute) * (3.78541 liters / 1 gallon)
There's a gallon on top (gallons/minute) and a gallon on the bottom (liters/gallon), so the gallons cancel out, leaving us with this:
(8.5 / 1 minute) * (3.78541 liters / 1)
(8.5 / 1) * (3.78541 / 1) liters / minute
32.175985 liters / minute
32.175985 liters / minute * (1 minute / 60 seconds)
32.175985 liters * (1 / 60 seconds)
about 0.5362664167 liters / second
Answer: About 0.5363 liters / second