Adding half-equations part 2
The alternative is to get equal numbers of electrons on each side
E.g. displacement of copper from one of its compounds by magnesium
½ equation : Mg(s) – 2e- Mg2+(aq)
½ equation : Cu(s) – 2e- Cu2+(aq)
+ (in this case) the reverse of : Mg(s) – 2e- + Cu2+(aq) Mg2+(aq) + Cu(s) – 2e-
Or Mg(s) + Cu2+(aq) Mg2+(aq) + Cu(s)
Looks harder but that depends on what they give you in the question...