Example of Similar Triangles

Question:
In triangle ABC below, AD = 3, BD = 4, DE = 6, and DE // BC, find BC = ? (let x = BC)
similar Triangles example
Solution:
In triangle ABC, since DE // BC, then angle ADE = angle ABC, angle A is in commom, so triangles ADE and ABC are similar. then
similar Triangles example
Rule used:
similar Triangles rules