Crank,

One of the easiest ways to fix a broken chain on a bike with gears is to use a KMC missing link. (single speed bikes require a masterlink) There are other brands of quick connectors also. I will tell you about the KMC. You will need to have a chain riviot tool. With your chain tool remove the broken part(s) of the chain. That is drive-out the center pin on each end of your chain. Leave your chain so each end is a male end or has the hole open so you can install your missing link. There are two parts to the missing link. Each look the same. Make sure your chain is routed correctly through your sprockets. Then insert the missing link into one end of the chain. Then install the other link into the other end of your chain in the opposite direction. When you do this you can then connect the two halves of the missing link together, with your hands. After they are connected, pedal the chain around so that the link is on the top of the drive train. Hold your rear wheel from turning with one hand, and put pressure down on your pedal with the other. This will cause the two halves of the link to lock or snap into their final position. This can be a permanant fix if your chain is still the correct length, after you have made the repair.