Since we're in an X forum, I'm assuming you're talking about a 6 or 7 seat X. Since the 6 or 7 seat X doesn't have an 11 setting for those vents... Please hold while I bite my tongue... Now that my tongue is bitten, when you look at the bottom of the A/C settings, there is a "Rear" section which only has three parts: "Auto", "Temp", and "Fan Speed". You need to set that fan speed in order to affect air flow to any side vent behind the driver compartment. You will also need to turn off "Auto" if your passengers aren't being detected (for instance, if they are animals and no seatbelts are latched).
ETA: For clarification, I mean animals literally. More specifically light pet animals that would not set off the weight sensors in the seats. Humans who are such "animals" that they don't use seat belts would still set off the weight sensors and presumably trigger the automatic rear A/C.