N2O4 ↔ 2NO2
The following system react as below when increase in pressure occurs
The equilibrium will shift towards the left (more N2O4 is produced)
Step-by-step explanation
When pressure increases the equilibrium shift toward the side of reaction with fewer moles of gas.
In the reaction of N2O4 ↔ 2 NO2 there is only 1 moles of N2O4 and 2 moles of NO2.
Therefore increase in pressure led to shift of equilibrium towards the left. ( more N2O4 is produced)