Answer
(a): $X \leftrightharpoons Z$
Work Step by Step
1. Calculate $K_c$ for the first and the second diagram, considering each chemical balanced equation; if they are equal, this is the correct equation.
(a) $$K_{c1} = \frac{3}{6} = 0.5$$
$$K_{c2} = \frac{4}{8} = 0.5$$
Therefore, the correct answer is (a): $X \leftrightharpoons Z$
