Answer
a. $$K_c = \frac{[H_2][Br_2]}{[HBr]^2}$$
b. $$K_c = \frac{[Br_2][NO]^2}{[BrNO]^2}$$
c. $$K_c = \frac{[CH_3Cl][HCl]}{[CH_4][Cl_2]}$$
d. $$K_c = \frac{[BrCl]^2}{[Br_2][Cl_2]}$$
Work Step by Step
The formula for the equilibrium constant expression is:
$$K_c = \frac{[Products]}{[Reactants]}$$
Also, the coefficients in the equation are the exponents of the concentrations.