Answer:
The equilibrium shifts to the left and more of NO₂ is formed.
Step-by-step explanation:
The Le Chatelier's principle states that when a form of stress is applied to a system in equilibrium, the system shifts so as to relieve that stress.
This principle explains that addition of one of the reactants to a system in equilibrium leads to the equilibrium shifting in such a way that the reaction occurring reduces the concentration of the added reactant.
In this case the addition of dinitrogen tetraoxide increases its concentration and therefore equilibrium shifts to reduce this concentration.