$\"\"$

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The angle is given by the circle C, $\"\"$ .

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$\"\"$ are a liner pair,and the angles of a linear pair are supplemantary.

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$\"\"$

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$

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$\"\"$

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$\"\"$ (Add 4 to each side)

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$\"\"$ (Simplify)

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$\"\"$ (Divide each side by 4)

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$\"\"$ (Simplify) $\"\"$

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Use the value of x to find $\"\"$ .

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The angle is given by $\"\"$ .

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$\"\"$ (Apply angle sum theorem)

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$\"\"$

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$\"\"$ (Substitute $\"\"$ )

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$\"\"$ (Subtract: $\"\"$ )

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$\"\"$ (Add: $\"\"$ )

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$\"\"$ . $\"\"$

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The value of $\"\"$ .