I am pretty sure the answer is DE = [tex]1 \frac{1}{4} [/tex]
Here's how I figured that out. Since AB, the smallest segment is [tex] \frac{1}{4} [/tex] of the whole segment, AC, that means all we have to do is use that fraction to find out the length of the DE.
So, EF, representing the whole segment, is equal to 5. Well, DE will equal [tex] \frac{1}{4} [/tex] of EF, so all we have to do is divide 5 by 4 to find our answer and our length for DE. That being said:
[tex] \frac{5}{4} = 1 \frac{1}{4} [/tex], which is our answer :)
I hope this helped! Have an amazing day :))
