We are given the following system of equations:

1. $-3x - y = 40$
2. $-x = -12$

Step 1: Solve one equation for a variable

The second equation, $-x = -12$, is easy to solve for $x$:

$-x = -12 \quad \Rightarrow \quad x = 12$

Step 2: Substitute the value of $x$ into the first equation

Now that we know $x = 12$, substitute this into the first equation:

$-3(12) - y = 40$

Simplify the equation:

$-36 - y = 40$

Step 3: Solve for $y$

Now, solve for $y$:

$- y = 40 + 36$

$- y = 76 \quad \Rightarrow \quad y = -76$

Final Answer:

The solution to the system is $x = 12$ and $y = -76$.

Solution as an Ordered Pair:

The solution is $(12, -76)$.

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Would you like more details or further clarifications? Here are 5 related questions for further practice:

1. Solve the system $2x + y = 10$ and $x = 4$ using substitution.
2. If $x = 5$, solve the equation $3x + 4y = 17$.
3. Use substitution to solve $4x + 2y = 14$ and $x = 3$.
4. Solve the system of equations $y = 2x - 1$ and $x + y = 7$ by substitution.
5. Solve $x - 3y = 9$ and $x = 2y + 4$ using substitution.

Tip: Always simplify equations first if possible to make the substitution process easier.