Start by writing the balanced chemical equation for this reaction
Notice that you have a
So, use nitrogen dioxide's molar mass to determine how many moles react
That many moles of nitrogen dioxide would produce
This would be equivalent to producing
This will be the theoretical yield of the reaction, i.e. what is produced when all of the moles of nitrogen dioxide react. This value corresponds to a 100% yield.
Now for the second part. You're told that the reaction actually produces 65 g of nitric acid, so the reaction's percent yield will of course be smaller than 100%.
SIDE NOTE Watch out for the number of sig figs you give for your values. I've used two sig figs for the answers, but I should have used 1 sig fig. For example, 80 g has only 1 sig fig, which means that the theoretical yield should be 70 g.
This will change the percent yield to 93%, so always keep an eye out for sig figs.