ANSWERS
x = 5
DE = 14
EF = 14
DF = 28
EXPLANATION
We have that E is the midpoint of DF.
This means that DE is the same as EF.
We have that:
DE = 2x + 4
EF = 3x - 1
=> 2x + 4 = 3x - 1
Collect like terms and solve:
3x - 2x = 4 + 1
x = 5
=> DE = 2(5) + 4 = 10 + 4
DE = 14
=> EF = 3(5) - 1 = 15 - 1
EF = 14
Since DE and EF lie on DF, we have that:
DE + EF = DF
=> DF = 14 + 14
DF = 28
