Answer:
The density of gasoline is 0.755 kg/L
ῥ_{gasoline} = 0.755 kg/L
And density is mass per volume.
ῥ = mass / volume
0.755 kg/L = mass / 14
mass = 0.755 x 14
mass = 10.57 kg
The mass in kilograms of 14.0 L of gasoline is about 10.57 kg. Note that this is just the rough value. As density of gasoline varies from 0.71 to 0.77 kg/L. SO the mass of 14.0 L of gasoline can be anywhere between 9.94 kg and 10.78 kg.