Jesus used this question to get the people to think about something that they already know. This can be written as a statement. AT: "We all know that a blind person cannot guide another blind person." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Some languages might prefer, "if one did." This is an absurd situation that is not likely to actually happen. (See: [[rc://en/ta/man/translate/figs-hypo]])
"A disciple does not surpass his teacher." Possible meanings are 1) "A disciple does not have more knowledge than his teacher" or 2) "A disciple does not have more authority than his teacher."