tablete-a
telefoane-b
14a........21b........1729lei|×2
28a.......45b.......3593lei
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28a........42b......3458lei
28a........45b.......3593lei
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3b.......135lei
135:3=45
1b=45
45×21=945
1729-945=784
784:14=56
1a=56lei
(am inlocuit in prima relatie ,poti inlocui si in a doua)