Subject

English/Spanish

To find the subject of a sentence always look for the verb first; the ask, who? or what? before the verb.  The answer will be the subject.
Teresa speaks Spanish.
Verb: speaks
Who speaks Spanish? Answer: Teresa.
Teresa is the subject.

Teresa's books cost a lot of money.
Verb: cost
What cost a lot of money? Answer: books.
Books is the subject.

If the sentence has more than one verb, you have to find the subject of each verb.
The boys were cooking while Mary set the table.
Boys is the subject of were.
Mary is the subject of set.