Answer: 
***If you found my answer helpful, please give me the brainliest. :) ***
Answer:
100m
Step-by-step explanation:
just subtract them from each other
500m
- 400m
-----------
100m
I would say the answer is 9. BUT again I'm not sure what your asking!
Answer:
a(10 - 13)
Step-by-step explanation:
The only common factor between these numbers is a, as 10 and 13 do not share factors (13 is prime). We can only factor out a.