Răspuns :
2C=3G
8C+9G=42
2C=3G=》 9G=6C
8C+6C=42
14C=42
C=42:14
C=3
2C=3G
2×3=3G
6=3G
G=6:3
G=2
NOTA: G= GĂINI
C= COCOȘI
2 cocosi cantaresc cat 3 gaini
4 cocosi ........................6 gaini
6 cocosi ......................9 gaini
8 cocosi .....................12 gaini
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8 cocosi .............9 gaini .......42 kg
12 gaini + 9 gaini = 42 kg
21 gaini cantaresc 42 kg
42 kg : 21 = 2 kg → cantareste o gaina
2 cocosi cantaresc cat 3 gaini = 3 x 2 kg = 6 kg
6 kg : 2 = 3 kg → cantareste un cocos
Verific: 8 × 3 kg + 9 × 2 kg = 24 kg + 18 kg = 42 kg