The sentence that correctly follows the rules for MLA in-text citations for a quote from page 9 of John Smith's book is the first one: The most common error in solving math questions "relates to the order of operations" (Smith 9).
MLA Style is generally used when writing papers in order to give credit for the information that has been taken from another source, that is to give credit for the ideas that belong to other people. The MLA Guide states that in-text citations consist in a quote that is included within quotation marks as well as the author's last name and the page number in parentheses and outside the quotation marks. The third option is incorrect because it includes the parentheses inside the quotation marks. Moreover, the period is always after the parentheses. For that reason, the second and last options are incorrect. In that way, the sentence that correctly follows the rules in the first one.