CoCl₂(aq) + Cd(s) → Cd²⁺(aq) + Co(s) + Cl^–(aq)

CoCl₂(aq) + 2 e^– → Co(s) + 2 Cl ^–(aq)

Cd(s) → Cd²⁺(aq) + 2 e^–

sum and eliminate electrons

CoCl₂(aq) + Cd(s) → Cd²⁺(aq) + Co(s) + 2 Cl ^–(aq)

This equation could have easily been balanced by inspection.