I can't help on this sorry math isn't my thing!!!!!!!!
100+(14.50•x) hope that helps
A. is your answer
you could always double check with a calculator
Theorem: If two chords intersect within a circle, then the product of the lengths of the segments (parts) of one chord is equal to the product of the lengths of the segments of the other chord.
In your case this theorem sounds as

If AM=7, MB=6, CM=8, then

Note that CD=CM+MD=8+5.25=13.25.
Answer: correct choice is C
I believe the slope is 0 because it they are both horizontal lines? I may be wrong though.