In this solution, I’ll be using the actual angles and names of the triangle so that you could easily see which areas within the given problem we’re working on.
In ΔKGH and ΔKJL, ∠GKH is common and ∠KGH = ∠KJL (corresponding angles)
⇒ Δ KGH ~ ΔKJL (AA criterion for similar triangles)
⇒ KG/KJ = GH/JL
⇒ 6/10 = GH/15
⇒ JL (x) = 9
Therefore, the correct answer is x = 9
