help me understand how can I solve these two. thank you.

Calculate H for the reaction 2C(s)+H2(g)C2H2(g) Given the following chemical equations and their respective enthalpy changes: 1. C2H2(g)+25O2(g)2CO2(g)+H2O(l)H=1299.6kJ 2. C(s)+O2(g)CO2(g)H=393.5kJ 3. H2(g)+21O2(g)H2O(l)H=285.8kJ Calculate H for the reaction NO(g)+O(g)NO2(g) Given the following information: 1. N(g)+O3(g)NO2(g)+O2(g)H=198.9kJ 2. O3(g)23O2(g)H=142.3kJ 3. O2(g)20(g)H=495.0kJ