Find x in the triangle

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The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

Nick has box brads. he uses 4 brads for the first project. nick let’s b represent the original number of brads and finds that for the second project, the number of brads he uses is 8 more than half the difference of b and 4. write an expression to represent the number of brads he uses for the second project.