Geometry Question?

Question

does anyone has a simple solution to find the θ?

see this
http://farm1.static.flickr.com/166/408616282_a4a27aa127.jpg

answer is θ=30'

Answer 1

Let D be the vertex between A and B.
Let E be the vertex between A and C.

Draw a perpendicular to AB through D. Reflect triangle BDE across this perpendicular. This reflection leaves D where it is, but gives us new points B' and E'.

Since angle DB'E' = angle DBE = angle A, we have B'E' parallel to AC. Therefore angle DEB = angle DE'B' = angle ACD = 30.