If they are all in a line then we can find the equation of their line using: y = mx + b
First find m using points (2,5) and (3,3)
m = (5-3)/(2-3) = 2/-1 = -2
Now using (3,3) and m= -2 to solve for b:
3 = -2(3) + b
3 = -6 + b
9 = b
So our equation is y = -2x + 9
That is the solution for question b)
Now to find the mystery point, solve:
1 = -2x + 9
-8 = -2x
4 = x
So our mystery point is (4,1)
So for part a) the answer is k = 4