Answer
$\frac{AB}{DB} = \frac{BC}{BF}$
Work Step by Step
We are given that $\triangle ABC$ ∼ $\triangle DBF$. In similar triangles, corresponding angles are congruent and corresponding sides are proportional.
Let us list the corresponding sides in the two triangles:
$AB ≅ DB$
$BC ≅ BF$
$CA ≅ FD$
The scale factor is the same for each set of corresponding sides. A proportion can be written that compares corresponding sides of the two triangles:
$\frac{AB}{DB} = \frac{BC}{BF}$
