Răspuns:
1) 1251+107-238=1358-238=1120
1+2+3+....+19=19·20/2=190
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2) 102- cel mai mic nr de 3 cifre distincte
98- cel mai mare nr de 2 cifre distincte
102+98=200
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3) a+b-c=(1957+234)+(1989-43)-(22+147)=2191+1946-169=3968
a-b+c=(1957+234)-(1989-43)+(22+147)=2191-1946+169=414
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4) a+7+b=37=>a+b=37-7=>a+b=30
(a+b)+5=30+5=35
a+(b+11)=30+11=41
47-(a+b)=47-30=17
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5) a+b+a-b=160
2a=160=>a=80
b= 0, 1, 2, 3..., 80
81 solutii are problema
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6) 16,61,25,52,34,43,70
