The formation of CH4 is given by
C(s) + 2H2(g)-----> CH4(g)
Δng for the reaction is -1.
ΔH = ΔU + ΔngRT
ΔH = -x -RT
where T is the temperature(which must be mentioned in the question)
R is gas constant (8.314 J/mol-K)
Hope it helps