Răspuns :
a + b = 7
b + c = 10
a + 3b + 2 c = a + b+ 2b + 2c =a + b + 2 ( b + c)=7 + 2 x 10 = 7 + 20 = 27
b + c = 10
a + 3b + 2 c = a + b+ 2b + 2c =a + b + 2 ( b + c)=7 + 2 x 10 = 7 + 20 = 27