( 1): 130 。 Because the middle is 50, then both sides are 40, so 40 * 2+50 = 130.

(2): 120 。 …………60,………………30,……30*2+60= 120

(3): AOC+BOC = 180。 Because AOB+COD= 180. And AOB+BOC+COD+AOD=360.

(4): 180/(7+29)= 180/3 1。

COB = 180 * 180/3 1 * 7/3 1

AOD = 180 * 180/3 1 * 29/3 1