Answer:
D. 20
Explanation:
Find the required diagram to the question in the attachment.
From the diagram it can be seen that the distance of the lines projecting from the centre of the circle to the line segment is equal i,e they are both 8. This means that the length of both chords given will be equal. For the known chord length, it can be seen that the line perpendicular to the chord cuts them at the centre. and since both sides of the chord are parallel, the other sides too will be 10 making the total length to be 10+10 = 20.
Since the length of the known chord is equal to the length of the unknown chord x, hence, the value of x will also be 20