Describe a combustion equation in general terms

A combustion reaction involves any fuel which can combine
with oxygen to produce both carbon dioxide and water.

The
general form is:

Fuel + O2 -->  CO2  + 
HOH

To balance a combustion reaction, use this
method:

Example reaction:   C4H8  + O2  -->  CO2  + 
HOH

1.  Balance the number of carbon atoms on both sides
using coefficients.

C4H8   +  O2  -->   4
CO2  +  HOH

2.  Balance the number of hydrogen
atoms on both sides of the equation using
coefficients.

C4H8  +  O2  -->  4 CO2  +
4 HOH

3.  Balance the oxygen atoms.  You have 8 oxygen in
the CO2 + 4 in the water for a total of 12 oxygen atoms on the right.  Divide the 12 by
2 ( you have two already on the left) and you get 6.

Now
complete balancing:

C4H8  + 6 O2 -->  4
CO2  + 4 HOH