apply law of mass action N2 +3H2 gives 2NH3 here pressure and temperature is constant so volume ratio and mole ratoi is similer so at equlibrium 1-x   5-3x  gives 2x total moles at eq is 6 -2x,molefrection of NH3 is 2x/6-2x which is equal to .426 so we calculate x and then apply mole frection formula with total P 1000atm and calculate Kp.