Treat compound antecedents joined by and as plural.
With compound antecedents joined by or or nor, make the pronoun agree with the nearer antecedent.
If one of the antecedents is singular and the other plural, as in the second example, put the plural one last to avoid awkwardness.
EXCEPTION:If one antecedent is male and the other female, do not follow the traditional rule. Usually you will need to recast the sentence.
Exercises:
Pronoun-antecedent agreement 1
Pronoun-antecedent agreement 2
Pronoun-antecedent agreement 3
Pronoun-antecedent agreement 4