13. the (number of voters) in the last primary election higher than usual.
a. was
b. were
c. are

14. neither the (cars) nor the trucks new tires.
a. has
b. have

13: A) was. 14: B) have.

Explanation: Subject-verb agreement means the subject and verb must have the same number (both singular or both plural). In the first sentence, the subject is "number of voters", "voters" is plural but "number" is singular, so the subject is singular, therefore the verb (also in singular form) would be "was." In the second sentence the subject is plural because they are talking about "cars" and "trucks" so the verb (also in plural) would be "have."