Extending network range
Can I use an 802.11g with an 802.11n? I would use the N as the primary and the G as the extended station.
Can I use an 802.11g with an 802.11n?
Unfortunately, these two products are not compatible if you are asking about Apple's "extend a wireless network" feature....to extend wirelessly.
Depending on which models of AirPorts that you have, you might be able to connect them together using an Ethernet cable to provide more wireless signal that way.