Ada yang bisa nomor 12, 13, 14, 15 ?? Tolong

12. 10 + 1/4 . 180 + 20 = 10 + 45 + 20 = 75° (C)

15. 1/2π + 1/6π + 1/12π + 1/20π + 1/30π
       = 30/60 π + 10/60π + 5/60π + 3/60π + 2/60π
       = (30+10+5+3+2)π/60 = 50π/60 = 5π/6    (C)