Explicație pas cu pas:
4 s z...........3 s c........440 kg /×3
3 s z............2 s c........320 kg/×4
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12 s z...... ..9 s c.........1320 kg
12 s z............8 s c........1280 kg
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1 s c........... 40 kg
4 s z + 3×40=440
4 sz +120=440
4 sz=440-120
4 s z=320
1 s z=320÷4
1 sz=80 kg