Answer:
x = 8
Explanation:
Chords AB and BD form an inscribed angle so <ABD = 5x
also given mAD = 80
Since inscribed angles are half the measure of their intercepted arc, angle <ABD is equal to 1/2(80 degrees), which is 40 degrees.
Now you have:
<ABD = 40
5x = 40
x = 8
Answer
x = 8