Here it is
[attachment id=0 msg=2785]
According to the question
A(g) +B(g) [attachment id=0 msg=2810] C(g)+D (g)
A B C D
Initial 2X X 0 0
Change -Y -Y +Y +Y
Equilibrium 2X-Y X-Y Y Y
3X/2 X/2 X/2 X/2
Now B and C are equal means
X-Y =Y
So X = 2Y
Y=X/2
Plug in value of Y in final equilibrium
K =[C][D] /[A]
K = (X/2)^2 /3X/2*X/2
Solve it