It only the last one.
Hope this helps :)
Given:
A line contains the points R(-1, 8), S(1, 4) and T(6, y).
To find:
The value of y.
Solution:
Three points are collinear if:

A line contains the points R(-1, 8), S(1, 4) and T(6, y). It means, these points are collinear.



Subtract 12 from both sides.

Divide both sides by 2.


Therefore, the value of y is -6.
I need a photo to help you
Answer:
We need to find the value of b to make 8b - 27 be equal to 5, so:
8b - 27 = 5
We solve the equation:
8b = 5 + 27
8b = 32
We divide both sides by 8:
b = 32/8 = 4
So now, we know that b=4, and we can verify:
8*4 - 27 = 5
32 - 27 = 5 TRUE