Răspunsuri

2014-02-12T21:16:25+02:00
(7+a)×3=35+a
21a+3a=35+a
3a-a=35-21
2a=14
a=7
Proba: (7+7)×3=35+7
           14×3=42
            42=42
Raspuns: peste 7 ani
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