Answer:
Ok so you want to find the relationship between triangle ADEe and ABC, so you can compare 2 corresponding sides. You have the lengths of AD and AB, so to find the relationship you can do AD/AB. AD = 3 and AB = 5, so that means the relationship is 3/5. Then, you can compare DE and BC. If BC is x, you would have:
3/5 = 6/x
so you know that 3/5 = 6/10, so x= 10
