Answer:
4.5
Explanation:
The Interesecting Secants Theorem states that when two secant lines intersect each other outside a circle, the products of their segments are equal. A secant is a straight line that cuts a curve in two or more points, so this definitely applies here, as both AB and CB interesect the circle twice.
Using this theorem, we can say that 6*3=4*x, so 18=4*x and x=4.5