Let us draw a picture to make the things more clear.
Attached is the image.
We have been given that

Therefore, we have

Now, in triangle bcd, we have

Now, in triangle acb, we have

Thus, ad is 15 cm.
Answer:
First differences means take the ordered pairs in increasing order for their x coordinates (assuming the x's go by ones), then subtract each y (except the last) from the y that comes after it. Keep doing that and you get the first differences. (The second differences would be what you get if you then subtract each of the first differences from the one that came after it (TMI probably but ...)
Say the points were (1,3), (2,7), (3,11) and (4,15). The first differences are
7-3 = 4
11-7 = 4
15 - 11 = 4 all 4. This would also be the slope. So that is the relationship - they are the same.
Answer:
The midsegment is one-half the length of the base
62.069% is what i thank it is