If there is more than one noun before the verb then learners of English (at least Vietnamese learners) are quite confuse whether the verb should be singular or plural. A plural verb is always used after subjects with “both ... and“.
Both the boy and the girl were considered very smart.
The verb is singular or plural, depending on the subject closest to the verb when “either ... or”, “neither ... nor”, or “not only ... but also” is used.
Neither the thief nor his aides were Vietnamese. (the plural noun is closest to the verb = used a plural verb)
Neither his aides nor the thief was Vietnamese. (the singular noun is closest to the verb = used a singular verb)
The nouns that follow the following expressions: along with, as well as, in addition to, and together with do not affect the verb. The subject alone is the one which determines whether the verb is singular or plural. Phrases with above mentioned expressions are normally set off by commas.
The thief, together with his aides, was ready to leave the country.
The aides, as well as the thief, were ready to leave the country.