Answer
$DF = 6\sqrt 3 \approx 10.39$
$DE= 6$
Work Step by Step
By the given Figure
$\angle F= 30^{\circ}$
So remaining $\angle F= 60^{\circ}$
FE= 12 given
Now by Theorem 5.5.2 / (30-60-90 Theorem)
$DF = 6\sqrt 3 \approx 10.39$
$DE= 6$