为如图所示, 已知, $\angle A=\angle F, \angle C=\angle D$.

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(1) 求证: $B D / / C E$;

(2) 已知 $\angle A B D: \angle D E C=2: 3$, 求 $\angle D E C$ 的度数.
$\because B D / / C E, D F / / A C$
$\therefore \angle A B D=\angle C, \angle D E C+\angle C=180^{\circ}$,
$\because \angle A B D: \angle D E C=2: 3$,
$\therefore$ 设 $\angle A B D=2 x, \angle D E C=3 x$,
$\therefore 2 x+3 x=180^{\circ}$,
$\therefore x=36^{\circ}$,
$\therefore \angle D E C=3 x=108^{\circ}$.