For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. If the conc

No problem, this isn't hard to do, believe it or not.

I'm assuming your question is:

For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. If the concentration of both products is 0.10 M at equilibrium, what is the concentration of the starting material, NOBr?

2NOBr(g) -> 2NO(g) + Br2(g)

The equilibrium constant is the product of the products over the product of the reactants, to the power of their coefficients. So the equilibrium coefficient is:

Kc = [NO]NOBr]²
2.0 = (0.001) / [NOBr]²
[NOBr]² = 0.001 / 2.0
[NOBr]² = 0.0005
[NOBr] = √0.0005
[NOBr] = 0.022 M

So the concentration of NOBr is 0.022 M. Hope I helped