Answer:
DE=3 cm
Explanation:
From the information we know, we can tell that triangle ABC is a scale factor of 2 from triangle DEF, because 10/5=2.
Side DE would be proportional to side AB.
Side AB is 6, so we would have to divide that by 2, because of our scale factor.
6/2=3.
Hope this helped! Have a good rest of your day!