Answer:
<DEF = 107
Explanation:
The way to best solve this problem is by starting with angle F. Remember that all angles in a straight line must add up to 180. So by subtracting 135 from 180 we get 45 for angle F.
180 - 135 = 45
After that, we can figure out the measure of <DEF. All the angles of a triangle must add up to 180. So:
180 - 28 - 45 = 107
Making the answer 107 for the measure of <DEF