In △ACB and △DCE,
∠ACB=∠DCE (Vertically opposite angles)
∠CAB=∠CED (Alternate angles to parallel lines AB and DE)
∠CBA=∠CDE (Alternate angle to parallel lines AB and DE)
Thus, △ACB≅△ECD,
hence, ACCE=CBCD (Corresponding sides)
615=BCCD
BCCD=25
Let BC=2x and CD=5x
Given BD=28
BC+CD=28
2x+5x=28
7x=28
x=4
Thus, BC=8 cm and CD=20 cm