Geometry needed ive completed part of it but i think its wrong can you check it and then on the last part !

1) midpoint of AB (point D)
x = (20+4)/2 = 24/2 = 12
y = (25+5)/2 = 30/2 = 15
answer D (12,15)your answer is correct

2)
slope CD = (15-6)/(12-30) = 9/(-18) = -1/2
answer
-1/2 your answer is correct

3)
equation of CD
slope = -1/2

equation in point slope form: y − y1 = m(x − x1)

using point C (30, 6)

y - 6 = -1/2(x - 30)

4) what is the option for CD?