Răspuns :
5ca + 4cr=720 / *3
4ca+3cr=570 / *4
15ca+12cr=2160
16ca+12cr=2280 le scadem
1ca=2280-2160
1ca=120
(caietul)
4ca+3cr=570
4*120+ 3cr=570
480+3cr=570
3c=570-480
3cr=90, cr=90.3
un creion = 30
5ca+4creioane=720g | x4
4ca+3creioane=570g | x5
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20ca+16creioane=2880g
20ca+15creioane=2850g
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/ +1creion = 30g
4ca+90=570g
4ca=480g
1caiet=120g
4ca+3creioane=570g | x5
-------------------------------
20ca+16creioane=2880g
20ca+15creioane=2850g
------------------------------------
/ +1creion = 30g
4ca+90=570g
4ca=480g
1caiet=120g