How many moles of oxygen are needed to burn 1.33 moles of methyl alcohol (CH3OH) ?

2CH3OH + 3O2 2CO2 + 4H2O

Well, it takes 3 moles of oxygen to completely burn 2 moles of methyl ...

So for every 2 moles of methyl, you need 1.5 times as much oxygen (3 divided by 2)

That makes your ratio 1 : 1.5

You need 1.33 moles of methyl so you multiply both sides of the ratio by 1.33 = 1.33 : 1.995

1.995 moles of oxygen are needed