Consider these chemical equations.

N2(g) + 3H2(g) → 2NH3(g)
C(s) + 2H2(g) → CH4(g)
4H2(g) + 2C(s) + N2(g) → 2HCN(g) + 3H2(g)

Which equation(s) do you need to reverse in order to calculate the overall equation for the formation of HCN and H2 from NH3 and CH4? Check all that apply.