Bike chain broke on my 21speed promax A series MGX,how do i replace it?

You can get a split link for around 50p to replace the broken one, this means you can remove the chain when ever you want with your bare hands no tools, how ever, to install one you will either need a chain tool or ask a bicycle shop to install one for your on your old chain, they should be able to do this within 5 minutes and charge you next to nothing. I have them on every chain i ever use on any bike, there's nothing like it.

You will need to first determine what the chain broke. If it is because of where you will need to replace the can with a new on. If it was anothe reason then you have a couple options.If you want to repair this yourself you will need to have a bicycle chain tool. Otherwise your local bicycle shop can reinstall the chain for a very low cost, less then the cost of a new chain tool.

If you are going to install it you can remove the bad link and reinstall the chain, however this will likely make you chain too short.

If you are going to replace the chain:
1. Lay the old chain out completely.
2. Cut the new chain the same length as the old chain. If using the quick link provided then make sure to cut the chain with two male ends and make it one link shorter then the original chain.
3.Start installing the chain from the rear derailleur. Start putting the chain in from the lower pulley(wheel on derailleur). Push over the lower pulley and under the upper pulley. Then back up behind and over the cassette (gears on the rear)
4. Now continue pulling the chain to the front. Go through the front derailluer and down around the chainrings.
5. Connect with the other end of the chain.
6.Use the quick link provided with the new chain or push the pin back into the chain (unless in is a shimano chain, then use the provided new pin)