hi guys im new to this and im in need of some help please. I have a bike with a single sproket on the front and 8 or 9 gears to use. it has a rear mech etc. my crank which joins onto the front chain ring has broken (where it bolts to the crank) . and i am wondering if this setup is correct ? i thought that it should have multiple rings on the front chainset? or a front mech ? can some1 please shed some light please !

Your bike has a fairly common system that many refer to as 1x9 (or 1x8). I don't know why or how your crank broke, but when you go to replace it you might consider going to a double or triple front. This will mean (other than the crank) buying a front derailleur and lever, possibly a new bottom bracket (the part the crank turns on), and also possibly a new rear derailleur (mech in Brit speak) depending on the capacity of what you have now.

The upgrades can be expensive, but the time to consider them is now. IMO if you've been happy with the 1x9 setup you have now, you probably should save the dough and simply replace the crank (if needed).

Ask about the options at a local shop, or bike co-op if there's one in your city.

If you can post a photo of the damaged area, we can offer more specific suggestions for repair or replacement.

Really no way for us to say what the bike "should" have. We can only help you with what is. It might have has a double/triple and a derailleur (mechanism) at one time, but there is nothing "incorrect" about a single front and 8-9 rear, and it has nothing to do with the crank arm problem. I agree we need some good pictures before we can advise further, as the way you are describing the problem is not clear.