Final answer:
The citation (Gantos 12) should be placed at the end of the sentence that contains the quote
Step-by-step explanation:
The correct placement for the citation (Gantos 12) to show that you included a quote from page 12 of a book by Ralph Gantos is at the end of the sentence that contains the quote. This is usually done within parentheses and before the closing punctuation mark of the sentence. For example, if the quote is "This is a quote from page 12" (Gantos 12), the citation would be placed at the end of the sentence like this.
Learn more about Citation placement in English writing