Answer
AB = 6
BC = 12
Work Step by Step
Since there are two congruent angles, triangles ABC and DEF are similar. Thus, we create proportions:
$\frac{AB}{2} = \frac{9}{3} \\ \frac{AB}{2} = 3 \\ AB = 6$
And:
$\frac{9}{3} = \frac{BC}{4} \\ \frac{BC}{4} = 3 \\ BC = 12$
