Answer:
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
