How do you balance these equations for reactions occurring in an acidic solution

Balance these equations for reactions occurring in an acidic solution.

(b) PbO2 + Cl- → PbCl2 + Cl2

(f) H2C2O4 + HNO2 → CO2 + NO

Please explain how you found the answer

PbO2(s) + 2Cl- + 4H+ + 2e- --> PbCl2 + 2H2O(l)
2Cl- --> Cl2 + 2e-
------------------------------ -------------------------------
PbO2 + 4Cl- +4H+ --> PbCl2 + Cl2 + 2H2O

H2C2O4 --> 2CO2 + 2H+ + 2e-
2(HNO2 + H+ + 1e- --> NO + H2O)
------------------------ --------------------------
H2C2O4 + 2HNO2 + 2H+ --> 2CO2 + 2NO + 2H2O + 2H+
simplify
H2C2O4 + 2HNO2 --> 2CO2 + 2NO + 2H2O