The mixing of one mole of A2 with 3 moles of B2 gives rise

I’m stuck on this question:Consider the following reaction at a certain temperature:A2 B2 <--> 2ABThe mixing of one mole of A2 with 3 moles of B2 gives rise to x moles of AB at equilibrium. The addition of two more moles of A2 produces another x mole of AB. What is the value of the equilibrium constant for the reaction?