Answer:
x=18
Explanation:
We know that triangle ABC is similar to triangle ADE, so therefore the proportions of their corresponding sides must be congruent.
We know that all of AD is 15 and BD is 5, which leaves AB to be equal to 10.
Next, we set up the following proportion: 10/12 = 15/x because they are corresponding sides of similar triangles divided by eachother.
Cross multiply and you will get 10x = 12x15 (180)
next, divide both sides by 10 to isolate x
x = 18