Answer:
x = 5
Explanation:
You want the length of x in the figure showing similar triangles.
Proportion
The bottom edge of the triangle is 2/3 of the left edge.
The similar triangles have the same ratio of side lengths. That means x is 2/3 of (3+4.5):
(2/3)(7.5) = 5
The length x is 5 units.