Răspuns :
[tex]\bf 15a-5b+3c = 586[/tex]
[tex]\bf 6b -14a -2c = 857[/tex]
_________________ (+) adunam cele doua relatii
[tex]\bf 15a-5b+3c +(6b-14a-2c) = 586+857[/tex]
[tex]\bf 15a-5b+3c +6b-14a-2c = 1443[/tex]
[tex]\boxed{\bf a+b+c = 1443}[/tex]
[tex]\bf 15a-5b+3c = 586[/tex]
[tex]\bf 6b -14a -2c = 857[/tex]
_________________ (+) adunam cele doua relatii
[tex]\bf 15a-5b+3c +(6b-14a-2c) = 586+857[/tex]
[tex]\bf 15a-5b+3c +6b-14a-2c = 1443[/tex]
[tex]\boxed{\bf a+b+c = 1443}[/tex]