(r,7), (11,8), m=-1/5 What is r?

Question

 Can you help me solve this I cant figure it out.

Answer 1

Use the slope formula:

 

m = (y₂-y₁)/(x₂-x₁)

 

-1/5 = (8-7)/(11-r)

-1/5 = 1/(11-r)

 

cross multiply:

 

-(11-r) = 5

r - 11 = 5

 

Can you finish it?