Agenerator needs a fixed amount of fuel to keep it running two hours a day. after running for 6 days, the generators fuel tank was 2/3 full. after 11 more days, 3 1/2 liters of fuel was left in the tank. if the tank was originally full, how much fuel can the tank hold?

63 liters

The amount of fuel used per day is ...

... (1 tank - 2/3 tank)/(6 days) = (1/3 tank)/(6 days) = (1/18) tank/day

Then the amount of fuel used after 6+11 = 17 days is

... (17 days)×(1/18 tank/day) = 17/18 tank

and the amount remaining is ...

... (1 tank -17/18 tank) = 1/18 tank = 3 1/2 liters

To find the tank size, we can multiply this result by 18:

... 1 tank = 18×(3 1/2 liters) = 63 liters