According to the search results, there are different answers to the question "what is 6x9?" depending on the context. Here are some of the answers found:

• In basic math, 6x9 equals 54.
• In book publishing, 6x9 refers to the trim size of a book, which is 6 inches wide and 9 inches tall.
• In photography, 6x9 can refer to the size of sheet film, which is 2.5" x 3.5" in Europe and 2.25" x 3.25" in the USA.
• In car audio, 6x9 refers to the size of car speakers, which are larger than typical round speakers and can produce a level of mid-bass quality that is impossible from smaller models.

Therefore, the answer to the question "what is 6x9?" depends on the context and the meaning of the term.