Answer:
-1.5
Step-by-step explanation:
The distance between S and T is
4 - -7
4+7 = 11
Divide this in half to find the midpoint
11/2 = 5.5
Add this to point S to get the point itself
-7 + 5.5 = -1.5
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.
It is 9:4.
Reason: divide both numbers by a common multiple, which is 7.