Math question that I don’t get

Question

b is the midpoint of segment ac on the cordinate plane. The coordinates of the 3 points are: A (-4, 5) B (x, 2) and C (9, y). What are the values of x and y

Answer 1

A(-4,5)

B(x, 2)

C(9, y)

B is the midpoint.

which means its x coordinate is the average of the A and C x coordinates

and its y coordinate is the average of the A and C y coordinates

x = the average of -4 and 9 = (-4+9)/2 = 5/2 = 2.5

2 is the average of 5 and y. (y+5/2) = 2

y+5=4, y =-1

B is (2.5, 2)

C is (9, -1)