How many atoms of carbon are needed to produce 0.45 mol aluminium? How many atoms of carbon are needed to produce $\pu{0.45 mol} ~\ce{Al}$?
  $$\ce{3C + 2Al2O3 -&gt; 4Al + 3CO2}$$ 


I am not sure where to start, whether or not I convert moles straight to atoms or convert moles to grams of $\ce{Al}$, then to moles of $\ce{C}$ and then to atoms? I tried the latter of my suggestions and ended up with $\pu{9.8E24}$, but  I don't know if this is correct.
The key to this is by examining the mole ratio. Your balanced equation shows that 4 mols aluminium: 3 mols carbon

If you are familiar with ratios from maths, you can therefore find the specific number of moles of carbon in this reaction.

$4\ce{Al}: 3\ce{C}\implies0.45\ce{Al} :~?$ 

I think you should be able to get the answer as 0.3375 moles of carbon (again, it's just ratios)! From here, you use moles = mass / mr to get your answer.