check my work?

Two lines or equations are described in each part. Decide whether each system has one solution, no solution, or infinitely many solutions. Show your work or explain your reasoning.

(a) Line a has a rate of change of 7. Line b has a rate of change of -7 .

 

b)These two graphed lines:

https://snag.gy/pIWfyK.jpg

 

c) Line c and line d are parallel.\

 

And I got for

a) one solution 

b) One solution 

c) no solution