An automobile gasoline tank holds 20 kg of gasoline. when the gasoline burns, 83 kg of oxygen is consumed and carbon dioxide and water are produced.

The total mass before the reaction equals the total mass after the reaction. Gasoline + O2 = CO2 + H2O. the law of the conservation of mass, the mass of the products must equal the mass of the reactants in a closed system. Therefore, assuming a closed system 20 kg + 82 kg = 102 kg = mass of reactants = mass of products.

Missing question: What is the total combined mass of carbon dioxide and water that is produced?

Chemical reaction: gasoline + O₂ → CO₂ + H₂O.

For this question use mass conservation law (mass of products is equal to mass of reagents) : m (reactants) = m (products of reaction).

m (gasoline + oxygen) = m (carbon (IV) oxide + water).

m (carbon (IV) oxide + water) = 20 kg + 83 kg = 103 kg.