Plural nouns treated as singular

Question

This is very confusing.  I have gotten it wrong in quizzes twice because I used a singular verb with the "plural" noun as in Mes vacances coûte.....please explain why I should use a plural verb? In the lesson all the examples show a plural noun (French style) with a singular verb. And, in the examples there are only singular verbs with the plural nouns.

Maarten Kamp · Accepted Answer

I don’t see any example with a plural noun as the subject of the verb with the verb conjugated in singular form. Can you indicate which examples are causing difficulty? I am sure this can be clarified.
Verb agreement is needed with grammatical ‘number’ of the (collective) subject noun 
- singular with singular collective nouns eg la famille/la police est .....
- plural with plural nouns eg les vacances/les toilettes sont ....
Adjective agreement also occurs with the nouns when applicable.