Answer:
the scale factor is 3/4
x = 16×3/4 = 12
Explanation:
the only side length we have for both triangles is the short left side.
we see that we get ED from SR and need to transform 4 into 3. how do we do that ?
well,
4×f = 3
f = 3/4
that is the scaling factor, as all side lengths in EDF are created by multiplying the corresponding side in SRT by the same scaling factor (3/4).
therefore,
x = EF = ST×f = 16×3/4 = 4×3 = 12