3. 3x + 7y = -63\nx - y = -1

Explanation:

Step1: Express x in terms of y from the second - equation

From $x - y=-1$, we get $x=y - 1$.

Step2: Substitute x into the first - equation

Substitute $x=y - 1$ into $3x+7y=-63$. Then $3(y - 1)+7y=-63$. Expand the left - hand side: $3y-3 + 7y=-63$. Combine like terms: $10y-3=-63$.

Step3: Solve for y

Add 3 to both sides of the equation: $10y=-63 + 3=-60$. Divide both sides by 10: $y=\frac{-60}{10}=-6$.

Step4: Solve for x

Substitute $y = - 6$ into $x=y - 1$. Then $x=-6 - 1=-7$.

Answer:

$x=-7,y=-6$