36 points + brainliest for correct & explained answer : )

When two triangles are similar, that means that the lengths of their sides are similar, meaning that if you were to multiply each side of one triangle by 'a magic number,' you would get the corresponding lengths of the other triangle. In this problem, the first step is to find the 'magic number.' Two sides that are corresponding are 6 and 8. Dividing them, we get that the magic number is 8/6 which is 4/3. That means to find the answer, we will have to multiply 9 by 4/3.
9 * 4/3 is 12, meaning that x is equal to 12 units.