Ok, so first realize that 2 of the NO (squarecircle) combine with 1 of the O2 (doublecircle).

There are 4 NO originally, this means that 4NO molecules * 2 NO2 molecules/2NO molecules=4NO2 molecules So we should have 4 NO2 molecules on the right hand side.

If we make 4NO2, how many O2 do we use? 4NO2 * 1O2/2NO2 = 2O2

Since 2O2 are used, we will have 5-2= 3 O2 left on the right.

So we will have: 4 NO2 (squarecirclecircle) and 3 O2 (circle circle) on the Right hand side.

We see that NO is the limiting reagent as it used up first and no more NO2 can be made after that. We still have O2 left so that is the excess reagent.