No. 6, pake cara tolong bantu ya

Besar sudut DOA = 180 – sudut DOC = 180 – 60 = 120
besar sudut BOC = 40
busur BC = 12

busur DC =
sudut DOA/BOC = DA/BC
120/40 = DA/12
40 x DA = 120 x 12
40 x DA = 1440
DA = 1440 : 40 
DA = 36