+128631 3a + b + c = -3
a + 3b + c = 9
a + b + 3c = -19
add these
5a + 5b + 5c = - 13
5 ( a + b + c) = -13
a + b + c = - 13 / 5
b + c = -13/5 - a
Subbing this into the first equation and simplifying we get that
2a = -3 + 13/5
2a = -2/5
a = -2/10
a = -1/5
Subbing this value into the swcond and third equations we have that
-1/5 + 3b + c = 9 ⇒ 3b + c = 9 + 1/5 ⇒ 3b + c = 46/5 ⇒ -9b - 3c = -138/5
-1/5 + b + 3c = -19 ⇒ b + 3c = -19 + 1/5 ⇒ b + 3c = -94/5⇒ b + 3c = -94/5
Add the last two equations and we have that
-8b = -232/ 5
b = -(232/ 5) (-1/8) = 29/5
And
b + c = -13/5 - a
29/5 + c = -13/5 -(- 1/5 )
29/5 + c = -12/5
c = -41/5
So
abc = (-1/5) (29/5) ( -41/5) = 1189 / 125
