It is given that the measurement of arc AC = 155 . And AB is the diameter, so measurement of arc AB=180 degree . Therefore arc BC = arc AB - arc AC = 180-155=25 . And the radius divides chord CD in two equal parts, so it divides the arc too in two equal parts. Therefore if the measurement of arc CB =25 , then the measurement of arc BD =25 too. Hence x =25 .
