-Thank you-

and

BC and EF are similar sides

So make a proportion

[tex]\sf{ \frac{AC}{DF} = \frac{BC}{EF} }[/tex]

Plug in the numbers

[tex]\sf{ \frac{9}{DF} = \frac{15}{25} }[/tex]

Cross multiply

[tex]\sf{DF \times 15 = 9 \times 25}[/tex]

Isolate DF and simplify it

[tex]\sf{DF = 15}[/tex]

And so your final answer is

[tex]\boxed{\bf{15 ~centimeters}}[/tex]