Find DF
Segment addition

Answer:
mDF = 18
Step-by-step explanation:
DE and EF must add up to DF.
Step 1: Set up equation
mDE + mEF = mDF
x + 7 + 7 = 4x + 2
Step 2: Solve for x
Step 3: Find mDF
mDF = 4x + 2
mDF = 4(4) + 2
mDF = 16 + 2
mDF = 18