Balancing half-reactions basic soln.

i know the steps and do not have problem doing these types on say br2+so2 -> br- + SO4^2-
but im a little confused at one i ran across O2(g)=>OH^-(aq)

Rules for balancing Redox equations:
O = -2, unless in peroxide, O = -1
H = +1, unless in metallic hydride, H = -1
All column 1 metals = +1
All column 2 metals = +2

1) Determine the oxidation state (charge) of each atom of each element.

2) Determine which element’s atoms have changed oxidation number from the left side of the equation to the right side of the equation.

3) Write the equation as 2 half-reactions. Include the particles (atoms, ions, molecules) which are involved in change of oxidation state.

4) Balance all atoms and ions, except O and H, with the use of coefficients.

5) To balance the O’s, add enough water (H2O) to the side deficient in O atoms.

6) To balance the H atom, add enough H+ to the side deficient in H atoms.

7) Balance the charge by adding electrons to the side deficient in negative charges.

8) Multiply the half-reactions by smallest whole numbers to balance electrons.

9) Add the 2 half-reactions and subtract any duplications.

If the reaction occurs in a basic solution, add the same number of OH-1ions to both sides to equalize the number of H+1 ions.

This method works well for oxidation reduction reactions.
I suggest that you make a copy of the steps above!
Balancing half-reactions basic soln.?
i know the steps and do not have problem doing these types on say br2+so2 -> br- + SO4^2-
know the steps and do not have problem doing these types on say

Br2 + SO2 → Br- + SO4^2-

In Br2, Br = 0; in Br-, Br = -1
In SO2, S = +4; in SO4^-2, S = +6

Step 3
Br2 → Br -1
SO2 → SO4 -2


Step 4
Balance Br by making 2 Br -1 on the right side. S is balanced.
Br2 → 2Br -1
SO2 → SO4 -2

Step 5 Balance O’s in the 2nd equation, by adding 2 H2O to left side.