2b-a
Answer Choices:
A)21
B)5
C)3
D)20

You haven’t given a photo of your work that you need help with...answer choices for what?
2b) you could be talking about Algebra ,line graph or even another subject.
So please if you need help put a photo

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm