Please help?

Step 1 : come up with the two half reaction.
1. CrO₃⁻ → CrO₄⁻
2. H₂O₂ → 2OH⁻

Step 2 : balance H and O atoms by adding H₂O and OH⁻.
1. CrO₃⁻ + 2OH⁻ → CrO₄⁻ + H2O
2. H₂O₂ → 2OH⁻ (already balanced)

Step 3 : balance the charge by adding electrons to the more positive side (less negative side).
1. CrO₃⁻ + 2OH⁻ → CrO₄⁻ + H2O + 2e⁻
2. H₂O₂ + 2e⁻ → 2OH⁻

Step 4 : Add the two half equations together, and eliminate 2e⁻ and 2OH⁻ on the both sides. The balanced equation is :
CrO₃⁻ + H₂O₂ → CrO₄⁻ + H2O