For this case we have the following system of equations:

We multiply the first equation by -1:

We have the following equivalent system:

We add the equations:

Equality is not fulfilled, so the system of equations has no solution.
Answer:
Option C
The unit rate is 5cm per 1min
5:1
Answer:
answer is A
Step-by-step explanation:
Answer:
B)
and C) 
Step-by-step explanation:
Once a linear function has a constant rate of change, you just have to find the linear functions. Also, the other ones are quadratic functions, and their graph are parabolas, which don't have a constant rate of change.
Considering 
has a constant positive rate of slope 2.

has a constant negative rate of slope -7
