The triangle proportionality theorem states that if a line parallel to a side of the triangle intersects the triangle, then the two sides are divided proportionally.
See the attached image. In
,
according to the theorem stated above.
Let's create ratios to solve for x in this problem.

- Cross multiply (12 * x + 4) = (9 * 2x).
12x + 48 = 18x
- Subtract 12x from both sides.
48 = 6x
x = 8