Step-by-step explanation:
such a scale factor applies to all sides and lines.
we see that DE is 12 units, and AB is 4 units.
so,
12×f = 4
f = 4/12 = 1/3 is the scale factor
control : check the other side
FE = 6 units
6 × 1/3 = 2
so, the corresponding side in the small triangle must be 2 units long.
and indeed, CB is 2 units long. all correct.
