Picking an inner tube size So I need to replace my inner tube as it got destroyed beyond any repair I can make (a hole right under the valve) but unfortunately I dont know what size the inner tube should be and I cannot figure out the different types of measurements of tubes. The metal part of the wheel has the markings 700x22 A/C, while the inner tube is too worn out to make out anything on it (Ive had it for like 2 years and I patched it 3 times :D )

The wheel is on the front and its a mountain bike, If that matters.
Look at the tire. it will have a size on the sidewall. Something like 29" x something or 26" x something or 700/700c x something. Tubes are sold with a range of sizes like 700c x 20 mm - 25 mm. You just need to be within the range (or close to it).

Alternatively, you'll find a number like ISO/ETRTO 20-622. The 622 is the wheel size in ETRTO standard (in this case, 700c for common people), and 20 is the tire size. So the above 700 x 20-25 mm would work here.

I'd guess that you're running a 29er with a 22 mm rim width, so you'll need a 29" x something tube. 

Also, check the valve -- the common ones are presta (little screw you have to undo to pump) and schrader (like a car). You'll want to match this with the rim (use whatever is in the rim already).