Q: Cannot connect my Lexmark cx310 wirelessly to my Macbook Air

See if your Lexmark printer is AirPrint compatible >  About AirPrint - Apple Support

if your device has it's own network card then the airport is unnecessary and ads overhead.

USB is by far the fastest and most direct way to connect to the printer on a single computer, but offers no other benefit if you USB to a wireless router.

You should connect the printer directly to the network via ethernet if it needs to be shared.

or directly to the Wi-Fi if ethernet is not an option.

http://www.lexmark.com/publications/pdfs/2007/x95x/en/info-you-need-to-set-up-pr inter-on-wireless-network-topic.html

Network Printer Troubleshooting

Ping printer: If you have the printers IP address open Terminal (Applications/Utilities) and at the prompt type: ping {printerIP}. You will get a reply or failure.

If you haven't done so already, try resetting the printing system.

Reset the printing system - OS X El Capitan

WiFi Printer to WiFi Network - Connect