Răspunsuri

2014-10-14T14:34:16+03:00
2014-10-14T14:35:01+03:00
A-b=6 ⇒ a=b+6
7×a-7×b+ x=55 ⇔ 7×(b+6)-7×b+x=55 ⇔ 7b+42-7b+x=55 ⇔ 42+x=55 ⇒ x = 55-42 ⇒ x = 13
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