12.a,b-lazi de mere
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a+b=35
b=a+5
inlocuim b cu a+5:
a+5+a=35
2xa=35-5
2xa=30
=> a=30:5
a=15 kg
b=15+5=20 kg
13.
a+b+c=20
a+b=c
=> b=c-a
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a+c=16 => c=16-a
c-a=b
inlocuim c cu 16-a:
b=16-a-a
b=16-2xa
=> a+16-2xa+16-a=20
=> 32-20=2xa
=> 2xa=12 => a=12:2
a=6 baloane are primul
=> c=16-6
c=10 baloane are al III-lea
b=16-12
b=4 valoane are al II-a
