How to solve

$14\mathrm{.}27.$ Carbon black is produced by the decomposition of methane:

$C{H}_4(g)C(s)+2H_2(g)$

For equilibrium at $650C$ and $1$ bar,

$($a$)$ What is the gas$-$phase composition if pure methane enters the reactor, and what fraction of the methane decomposes?