Solve: 18 squared + x squared= 30 squared

To describe a sequence of transformations that maps triangle abc onto triangle a"b"c", a student starts with a reflection over the x-axis.how should the student complete the sequence of transformations to map triangle abc onto triangle a"b"c"? plz

How do i do this activity, is appreciated

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