To solve the linear system using substitution, the first step is to solve one of the equations for one of the variables.

Given the system:

1. $y = -3 - x$
2. $3x + y = 3$

The first equation, $y = -3 - x$, is already solved for $y$.

First Step: Substitute $y = -3 - x$ into the second equation.

So, replace $y$ in the second equation:

$3x + (-3 - x) = 3$

Now, you can solve for $x$.

Would you like to proceed with the solution, or do you have any questions?

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Here are 8 related questions to expand your understanding:

1. How would you solve for $x$ after substitution?
2. What is the next step after finding the value of $x$?
3. Can substitution be used for nonlinear systems?
4. How do you check if the solution is correct?
5. What if both equations were already solved for $y$?
6. How does substitution compare to the elimination method?
7. What happens if the system has no solution?
8. How would you graphically interpret the solution?

Tip: Always simplify the equations as much as possible before starting the substitution method. This makes the process easier.