Answer and Explanation:
A combustion reaction occurs in the presence of oxygen (O2),and it gives carbon dioxide (CO2) and water (H2O) as main products.
So, in each case, we have to write O2 in the reactants side (with the given hydrocarbons), while CO2 and H2O will be in the products side:
a. Butane (C4H10):
The equation is balanced because in each side of the reaction there are: 8 C, 20 H and 26 O.
b. Cyclohexane (C6H12):
The equation is balanced because in each side of the reaction there are: 6 C, 12 H and 18 O.