Which direction would the equilibrium shift, CH4 + 2H2S = CS2 + 4H2. When increases the pressure on system?

The equilibrium would shift to the right, towards the products CS2 and H2, in order to decrease the pressure on the system. This is because there are fewer moles of gas on the product side compared to the reactant side, so shifting to the right would decrease the total pressure of the system.

Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.

In this case, increasing the pressure on the system will shift the equilibrium to the side with fewer moles of gas. The reaction has 3 moles of gas on the left and 6 moles of gas on the right. Therefore, the equilibrium will shift to the left, favouring the formation of CH4 and 2H2S.