Can i sync two IPhones with one Itunes/computer?

I have a Iphone 3 and 4 and am wondering if i can sync them to the same itunes/computer without deleting any apps or contacts or music.

Syncing and backing up your information is always a good idea to do. But your question is whether or not you can sync two devices at a time?
Well the answer is, "Yes." It is possible and there's no danger involving this process if that's your concern.iTunes has made it easy for this, knowing everyone has different taste for different things.
Just remember to go to the "Preferences" section to edit specific things for each device.

You can if you have 2 usb cords that can plug in the computer and they should both be seen under iTunes then you can sync both

Hope I helped.

Yes, you can sync any number of iPhones, iPods and iPads with your computer and iTunes using your iTunes Account. You just need to connect your device with the computer and enter in your iTunes account, then sync your device…