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

Prove: x=9

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