We'll talk about number here, and look at case another time. This is increasingly being accepted, but it's rarely necessary. Sometimes, you can avoid the problem by rewriting.
Mixed number is also common with collective nouns like group , team or couple .
Because these things involve more than one individual, we tend to use plural verbs with them - but really, they are entities in themselves and are therefore singular. If there's a plural noun immediately before the verb, the verb tends to be incorrectly made plural as well, even though that noun isn't its subject. In our last issue, we talked about agreement in number and promised that next time, we'd look at agreement in case. Case' refers to the different forms that nouns, adjectives and pronouns can take to show their relationship to other words in the sentence. If that sounds daunting, it helps to know that in English, only two case forms have survived, and only in the personal pronouns.