My husband owns a weed eater lawn tractor, and he broke the belt that runs the blades.
The manual that he has dose not say anything about belt tensions would anybody know?
Please help.

Look for the model number on the mower, and call any mower repair shop. They can get you a belt replacement number. You can also go online with this info. Just type in "lawn mower parts" and you can get a number of places to find belts. The belt itself just runs around pulleys to help guide it, with the engaging pulley holding tension on it. There is no adjustable limit to it. Hope this helps.