According to the ideal gas equation-

**PV = nRT**

**P = n/V x RT**

P = CRT where C is **molarity **

P_{A} = C_{A}RT = [A] x RT

P_{B} = C_{B}RT = [B] x RT

P_{C} = C_{C}RT = [C] x RT

P_{C} = C_{D}RT = [D] x RT

Put the value of P_{A}, P_{B}, P_{C} and P_{D }in the equation

**K**_{p} = [C]^{c} (RT)^{c} [D]^{d} (RT)^{d} / [A]^{a} (RT)^{a} [B]^{b} (RT)^{b}

**K**_{p} = [C]^{c} x [D]^{d} / [A]^{a} x [B]^{b} x (RT)^{c+d-a-b}

**K**_{p} = K_{c} x (RT)^{Δ}^{n}

Where **Δ**n there is a *difference of the number of molecules of the products and the reactants*.