Answer:
arc BC = 75 degrees
Step-by-step explanation:
The angle where chords cross is half the sum of the intercepted arcs. This relation can be used to find x and the angle and arc measures.
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The angle relation is ...
1/2((8x +11) +(9x -7)) = (8x +6)
17x +4 = 16x +12 . . . . . . . multiply by 2 and simplify
x = 8 . . . . . . . . . . . . . . subtract 16x+4 from both sides
Then the measure of arc BC is ...
arc BC = 8x+11 = 8(8) +11 = 75 . . . degrees
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Additional comment
We can compute the other measures just to make sure they have the desired relationship.
angle BAC = 8x+6 = 70 . . . degrees
arc FD = 9x -7 = 65 . . . degrees
Since 70 = (65 +75)/2, these measures work out as expected.
