no 12-21 apa ?? tolong banget

11. 1 3/4 : 2 1/4 : 14/9 = 7/4 : 9/4 : 14/9 = 1/2 (b)
12. 5/6 + 8/10 = 25/30 + 24/30 = 49/30 
      3 3/4 - 25/100 = 15/4 - 25/100 = 375/100 - 25/100 = 35/10 
      35/10 - 49/30 = 105/30 - 49/30 = 56/30 = 1 26/30 = 1 13/15 (c)
13. 0,56 = 56/100 = 14/25 (b)
14. MTK = 30%
      IPA = 0,25 = 25%
      IPS = 9/20 = 45/100 = 45%
     paling singkat = IPA, MTK, dan IPS (c)
15. ayam = 8/3 x 39 ekor = 104 ekor 
      itik = 5/3 x 39 ekor = 65 ekor 
     jumlah = 104 ekor + 65 ekor = 169 ekor (b)
16. 137 cm =137 : 100 = 1,37 m
      28 dm = 28 : 10 = 2,8 m
      = 1,37 m + 2,8 m + 1,2 m = 5,37 (c)
17. 0,2 ton = 2/10 x 1000 = 200 kg
      1,2 kuintal = 12/10 x 100 = 120 kg
      = 200 kg - 120 kg = 80 kg + 75 kg = 155 kg (c)
18. 17. 25 - 15.10 = 2 jam 15 menit
       MTK = 1 jam 15 menit 
       IPA = 2 jam 15 menit - 1 jam 15 menit = 1 jam = 60 menit
              = 60 menit - 10 menit = 50 menit (a)
19. 5 gros 4 lusin = (5 x 144) + (4 x 12) = 720 + 48 = 768
      12 lusin = 12 x 12 = 144 
      1 gros 14 buah = (1 x 144) + 14 = 144 + 14 =  158
      = 768 - (144 + 158) = 768 -  302 = 466 piring (b)
20. 4.500 cm^3 = 4.500 : 1000 = 4,5 liter
      = 5,25 liter + 18 liter = 23,25 liter
      = 23,25 liter - 4,5 liter = 18,75 liter (b) 
21. w = j : k 
         = 4.000 m : 200 m/menit = 20 menit (b)