faulty parallelism is a grammar construction where there is no balance in the parts of a sentence they have a similar meaning but the grammar structure is not equivalent.
the correct version of this faulty parallelism in the sentence is:
jefferson wrote the declaration of independence, and he was the nation's third president.
the problem with the first version is that the sentence:
"jefferson was both the writer of the declaration of independence"
presents jefferson as both a subject and an agent for the verb "write" because if he was "the writer" then the declaration of independence was written by him, besides that fact, the sentence presents a dependent clause.
while the second sentence:
he was the nation's third president.
presents a basic subject+verb+object structure
so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in both sentences:
jefferson wrote the declaration of independence, and he was the nation third president.
