In this question, you are given the gasoline density (0.749g/ml) and the gasoline volume (19.2 gallons). You are asked the mass of the gasoline in pounds. Then you need to convert the grams into pounds and the ml into gallons. The calculation would be:
mass of gasoline= gas density * gas volume
mass of gasoline= 0.749g/ml * (1 pound/453.592grams) * 3785.41ml/gallon * 19.2 gallon= 120 pounds