How do I solve for x?

We will use the thales's theorem to solve for x

Let ? be x

then, the other segment on the same line as x will be 20 - x since the line is 20 units long

According to thales's theorem:

"If a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio"

Hence, we can write that,

9 / 3 = 20-x / x

3x = 20 -  x

4x = 20

x = 5 units

Hence, the length of the line segment marked as '?' is 5 units

the answer is b.

64

step-by-step explanation:

c=2πr=2·π·8≈64