How do I skip back 5/30 seconds in itunes?

You can click-hold on the Previous button. It goes back in increments (starting at about 5 seconds), which increases as you continue to hold down the click, until you release. You can also do this action with the Next button (to "fast forward").

As a general tip: as long as you have an iTunes window up, in addition to holding previous/next buttons (which I somehow manage to screw up sometimes), you can also get iTunes to reliably do a simple 5-second jump by using:

⌘ + ⌥ + ←/→

Cmd+Option+Arrow [right or left] to go forward/backward respectively in 5 sec intervals.

How is it not easy? 🙂

It works in a similar way on the iPhone. On the Now Playing screen showing the song, it has the same type of Previous and Next buttons. Tap-hold on button to fast-backward or fast-forward, and release at desired location.

I have the same problem, but with iPad video. I watch lectures at the gym and want to skip back 30 seconds. There seems to be no way to do that in Apple's video program. (I can do it in some other programs where I'm not using iTunes video.) This seems so elementary-swipe left to go back, swipe right to fast forward, swipe up to increase volume, etc. Am I missing something here?