What is the length of DE ?? Thx :)

A; 10

Step-by-step explanation:

What we can see here is that the triangles are similar.

Hence, the ratio of their sides are equivalent.

Thus, mathematically;

ED/BA = DF/AC = BC/EF

what we want to calculate is ED = x

Thus;

x/15 = 12/18

Cross multiply;

18 * x = 12 * 15

18x = 180

x = 180/18

x = 10

its 4 because 2 times 2 is 4, if you double the number two you get four