12) -3x - 8y = 20\n-5x + y = 19

Explanation:

Step1: Isolate y in the second - equation

From $-5x + y=19$, we get $y = 5x + 19$.

Step2: Substitute y into the first - equation

Substitute $y = 5x + 19$ into $-3x-8y = 20$. Then $-3x-8(5x + 19)=20$. Expand the left - hand side: $-3x-40x-152 = 20$. Combine like terms: $-43x-152 = 20$. Add 152 to both sides: $-43x=20 + 152$, so $-43x=172$. Divide both sides by - 43: $x=-4$.

Step3: Find the value of y

Substitute $x = - 4$ into $y = 5x + 19$. Then $y=5\times(-4)+19=-20 + 19=-1$.

Answer:

$x=-4,y=-1$