А,
С
X = [?]°
55°
D
B
Х
E
→F
Angles are not drawn to scale.
Enter

Answer:
[tex]\displaystyle 35[/tex]
Explanation:
Complementary Angles sum up to ninety degrees, so do the following:
[tex]\displaystyle 90° = 55° + m\angle{DEF} \\ \\ 35° = m\angle{DEF}[/tex]
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