Answer:
Part A: Option A
Part B: Option C
Explanation:
Given two points (7, 5) and (21, 15)
we have to find the slope of the line passing through above two points.
The slope of line can be calculated as


Option A is correct.
Part B: Also given another line with a slope that is one-third that of the slope of above and passes through the origin and the point
we have to find the point.

The equation of line becomes



The point which satisfies the above equation passes through the line.
Not satisfied
Not satisfied
Satisfied
Not satisfied
Hence, the line passes through the point (21, 5)
Option C is correct.