Hello:) how to do question 6? :) I’m not sure which property to use :/

Answer:
which grade are you in so that i can tell you according to that
i, vì AD//BC nên góc A +góc B =180°
ii, góc A=góc B nên góc C=góc D -> ABCD là hình bình hành
And AB=BC=> ABCD là hình thoi