Solve using substitution. \( \begin{array}{l}-3 x-3 y=12 \\ y=-7\end{array} \)

Solve the system of equations by following steps: - step0: Solve using the substitution method: \(\left\{ \begin{array}{l}-3x-3y=12\\y=-7\end{array}\right.\) - step1: Substitute the value of \(y:\) \(-3x-3\left(-7\right)=12\) - step2: Multiply the numbers: \(-3x+21=12\) - step3: Move the constant to the right side: \(-3x=12-21\) - step4: Subtract the numbers: \(-3x=-9\) - step5: Change the signs: \(3x=9\) - step6: Divide both sides: \(\frac{3x}{3}=\frac{9}{3}\) - step7: Divide the numbers: \(x=3\) - step8: Calculate: \(\left\{ \begin{array}{l}x=3\\y=-7\end{array}\right.\) - step9: Check the solution: \(\left\{ \begin{array}{l}x=3\\y=-7\end{array}\right.\) - step10: Rewrite: \(\left(x,y\right) = \left(3,-7\right)\) To solve the system of equations using substitution, we have the following equations: 1. \( -3x - 3y = 12 \) 2. \( y = -7 \) ### Step 1: Substitute the value of \( y \) From the second equation, we know that \( y = -7 \). We can substitute this value into the first equation. ### Step 2: Substitute into the first equation Substituting \( y = -7 \) into the first equation: \[ -3x - 3(-7) = 12 \] ### Step 3: Simplify the equation Now, simplify the equation: \[ -3x + 21 = 12 \] ### Step 4: Isolate \( x \) Next, isolate \( x \): \[ -3x = 12 - 21 \] \[ -3x = -9 \] ### Step 5: Solve for \( x \) Now, divide both sides by -3: \[ x = 3 \] ### Final Solution Thus, the solution to the system of equations is: \[ (x, y) = (3, -7) \]