Answer:
DF = 13.5
Step-by-step explanation:
If the triangles are similar, the proportion between their corresponding sides is constant, so, if BC is corresponding to EF and AC is corresponding to DF, we get:
So, replacing EF by 6, BC by 4, and AC by 9, we get:
Then, we can solve for DF:
Therefore, the length of side DF is 13.5