NO react with oxygen to form NO2
that is 2NO +O2 --->2NO2
from the reaction above two moles of NO react with one mole of O2 to form two moles of NO2
The reacting ratio of NO to NO2 is 2:2 or 1:1 in simple terms
since ratio is 1:1 the moles of NO reacted is also 4.67moles