zy+xy=180 (angles on a line =180)
120(zy) + xy=180
now the other line's angles are xy, wx and kw which will all equal 180
you know that xy=60, wx=55, kw=?
which all add up to = 180 (angles on a line =180)
55(wx) +65(kw) = 120(zy)(vertically opposite angles are =)
Hope that helped?