tolong dijawab no.12 please nanti saya jadikan terbaik

180-72 = 108°
72° = 12 cm
108 = ...
108/72 = 3/2 x 12 = 18 cm

Lingkaran

Panjang busur AC/sudut AOC = panjang busur BC / sudut BOC
AC/(180-72) = 12/72
AC/108 = 1/6
AC = 1/6 x 108
AC = 18 cm