Given: ∠DFE = ∠CDF, CF ǁ DE, FG=2x, DG=18

Prove: x=9

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CE bisects DF at G
CD ǁ FE
Given
Definition
∠DFE = ∠CDF, CF ǁ DE, FG=2x, DG=18
x=9
Equal alternate interior angles mean parallel lines
Definition
FG = DG
CDEF is a parallelogram
2x=18
Substitution
Algebra
The diagonals of a parallelogram bisect each other