Answer:
x = 192
Explanation:
The three right triangles in the figure are all similar, so their sides are proportional.
Proportion
The length marked x is the long side of the smallest triangle, and the short side of the middle-size triangle. The long side of the middle-size triangle is ...
400 -144 = 256
We now have enough information to write the proportion ...
long side/short side = x/144 = 256/x
Multiplying by 144x gives ...
x² = (144)(256)
x = √(144×256) = 12×16 = 192
The length x is 192 units.