কোণ ঝামেলায় জড়ালে

Tried this problem my best,drawed line segment parallel to BC.,but couldn’t find any way to solve this.Can anyone help plz?

Just do some angle calculation and think.I got my answer like this .

You guys can continue a constructive conversation about it in the thread embedded under the problem description. Other people might be benefitted by that as well since it will be easier to find.