Răspuns :
a + b = 5 si b + c = 7
2 a + 5 b + 3 c = 31
= 2 a + 2 b + 3 b + 3 c =
= 2 ( a + b ) + 3 ( b + c ) =
= 2 × 5 + 3 × 7 =
= 10 + 21 =
= 31
a + b = 5 si b + c = 7
2 a + 5 b + 3 c = 31
= 2 a + 2 b + 3 b + 3 c =
= 2 ( a + b ) + 3 ( b + c ) =
= 2 × 5 + 3 × 7 =
= 10 + 21 =
= 31