Answer:
see explanation
Step-by-step explanation:
from the diagram
DF = DE + EF , that is
4x + 2 = x + 7 + 7
4x + 2 = x + 14 ( subtract x from both sides )
3x + 2 = 14 ( subtract 2 from both sides )
3x = 12 ( divide both sides by 3 )
x = 4
Then
DE = x + 7 = 4 + 7 = 11
DF = 4x + 2 = 4(4) + 2 = 16 + 2 = 18
