Answer:
7. Don't consider running a marathon unless you are in good physical condition.
8. Don't leave training until just before the marathon in case you might injure yourself.
9. Take time off from running every week otherwise, your body will not have a chance to rest.
10. As long as you train carefully, you can avoid injury.
11. Assuming you are sensible, you should run a marathon safely and successfully.
Explanation:
Rewriting the sentence using the words given in the brackets means structuring the sentence to retain the meaning but make a new sentence. The new sentences after their restructuring are given as below-
7. Don't consider running a marathon unless you are in good physical condition.
8. Don't leave training until just before the marathon in case you might injure yourself.
9. Take time off from running every week otherwise, your body will not have a chance to rest.
10. As long as you train carefully, you can avoid injury.
11. Assuming you are sensible, you should run a marathon safely and successfully.