The points (3,-23) and (8,r) lie on a line with slope 4. Find the missing coordinate r

Question

What’s the answer and explanation as I can not solve this problem

Answer 1

How do you find slope?

 

(-23 - r)/(3 - 8) = 4

(-23 - r)/-5 = 4

-23 - r = -20

-r = 3

r = -3