Answer:
x = 3
Step-by-step explanation:
Two secants drawn to a circle from an external point, then
The product of the measures of the external part and the whole of one secant is equal to the product of the external part and the whole of the other secant.
Thus
x × 12 = 4 × 9
12x = 36 ( divide both sides by 12 )
x = 3
