3. Dacă a+b=3,7 şi b+c=7,3, atunci a + 2b+c= 10..

Răspuns:
[tex]a+b=3,7\\\\b+c=7,3\\\\a+b+b+c=a+2b+c=3,7+7,3=11\\\\a+2b+c=10-fals[/tex]