Determining the equilibrium constant This is freely translated, I hope it's not too bad.

The reaction to dehydrate methylcyclohexane to toluene in the gaseous phase:

Formulate the reaction equilibrium's constant.

Now, that's not a problem - the problem is that I don't know the aggregate state. I know that $\ce{H2}$ is a gas and that other thing left of it seems to be toluene, which is also a gas according to the text above. So how should I now know what aggregate state the methylcyclohexane is in? I also assume everythings at standard conditions.
The solution is apparently (but it might be wrong, since it's not an official solution)

$$K_1 = a_\ce{C7H14}^{-1}\cdot a_\ce{C7H8}^1\cdot a_\ce{H2}^3 = \left(\frac{c_\ce{C7H14}}{c^\circ}\right)^{-1}\left(\frac{c_\ce{C7H8}}{c^\circ}\right)^{1}\left(\frac{p_\ce{H2}}{p^\circ}\right)^{3}$$
$$K_2=a_\ce{C7H14}^{1}\cdot a_\ce{C7H8}^{-1}\cdot a_\ce{H2}^{-3} = \left(\frac{c_\ce{C7H14}}{c_\ce{C7H8}}\right)^1\left(\frac{p_\ce{H2}}{p^\circ}\right)^3$$

whereas $K_1$ is right and $K_2$ is left.
I mean that's clear and everything but how do I know the aggregate state of $\ce{C7H14}$?
The standard for equilibrium constants of gas phase substances is to use $K_p$, so in this case $p^\circ$ would be more appropriate than $c^\circ$ for the organics as well as the hydrogen. If you use $c^\circ$, you should use it for all gas phase components and indicate your $K$ as $K_c$. Using different standards for gas phase components in the same reaction is unorthodox. 
And if you use your equilibrium constant for calculation of $\Delta G$ for example, the simple form of the equation $\Delta G^\circ = -RT\ln K$ requires that the $K$ be $K_p$ for gas phase reactions. Using $K_c$ will give an incorrect result.