On the basis of thermochemical equations (i), (ii), and (iii), find out which of the algebraic relationships given in options (a) to (d) is correct:

(i) C(graphite) + O2(g) → CO2 (g) ; ∆rH = x kJmol-1
(ii) C(graphite) + \(\frac{1}{2}\)O2(g) → CO(g) ; ∆rH = y kJ mol-1
(iii) CO(g) + \(\frac{1}{2}\)O2(g) → CO2(g); ∆rH = z kJ mol-1

1. z=x+y

2. x=y-z

3. x=y+z

4. y=2z-x