The following number lines are missing some numbers. Use the information provided to complete the number lines.  

1. 

   Hint (a):

   Start by finding the difference for one space.

   Hint 2(a):

   To do this, find the difference between the two given numbers and divide that by the number of spaces between them.

   More Help (a):

   The difference between $-12$ and $6$ is $18$.

   $\frac{18}{3}=6.$

   The difference for one space is $6$.

   Answer (a):

   

   The number line has been filled in above for you.

2. 

   Hint (b):

   Follow the steps in part (a).

   More Help (b):

   The difference between $0$ and $−27$ is $27$.

3. 

   Hint (c):

   Follow the steps in part (a).

   Answer (c):

   

4. 

   Hint (d):

   Follow the steps in part (a).