What is the usual oxidation state of aluminium, in their compounds?

For the equation given below, give the oxidation state for each element present in the equation.

$2\mathrm{Fe}+3{\mathrm{Cl}}_2 \to 2{\mathrm{FeCl}}_3$

Many people cook with natural gas, which is mainly methane, ${\mathrm{CH}}_4$. The equation for its combustion is : 

${\mathrm{CH}}_{4\left(\mathrm{g}\right)}+2{\mathrm{O}}_{2\left(\mathrm{g}\right)} \to {\mathrm{CO}}_{2\left(\mathrm{g}\right)}+2{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}$

Justify that this reaction is a redox reaction on the basis of change in oxidation states.