Have a cracked front brake hose on my b5 a4. How to I go about loosening the end that connects to the main hard line. I attached a photo. Is there a write up or diy?

 

Buy a flare wrench and undo the nut. It's mounted in a weird way which is probably confusing you but you'll figure it out once you loosen it.

 

I bought a nice set of metric flare nut wrenches specifically for that sort of thing, and I have yet to use them.

 

The hose end is held captive in that bracket by two tabs that protrude into the bracket. You'll need an 11mm or 7/6" flare wrench. When buying, try to find ones where the hex part extends all of the way to the face of the wrench. Many times they are dished inward for whatever reason and it makes getting a good bite on those fittings difficult.