1 Answer

Burseaner · Answer 1 · 2021-04-11T03:21:27+0000

Answer:

15

Explanation:

Consider right triangle EFD. The sum of the measures of all interior angles in triangle EFD is 180°, so

$m\angle FED=180^(\circ)-90^(\circ)-3x=90^(\circ)-3x$

Consider right triangle EBC. The sum of the measures of all interior angles in triangle EBC is 180°, so

$m\angle BCE=180^(\circ)-(90^(\circ)-3x)-90^(\circ)=3x$

Consider triangle ACD. The sum of the measures of all interior angles in triangle ACD is 180°, so

$x+8x+3x=180^(\circ)\\ \\12x=180^(\circ)\\ \\x=15$

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