Questions: Use the substitution method to solve the system 9x - 3y = 12 y + 6 = 2x

Use the substitution method to solve the system

9x - 3y = 12
y + 6 = 2x
Transcript text: Use the substitution method to solve the system \[ \begin{array}{l} 9 x-3 y=12 \\ y+6=2 x \end{array} \]
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Solution

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Solution Steps

To solve the system of equations using the substitution method, follow these steps:

  1. Solve one of the equations for one variable in terms of the other variable.
  2. Substitute this expression into the other equation.
  3. Solve the resulting equation for the single variable.
  4. Substitute back to find the value of the other variable.
Step 1: Solve the Second Equation for \( y \)

Given the system of equations: \[ \begin{array}{l} 9x - 3y = 12 \\ y + 6 = 2x \end{array} \]

First, solve the second equation for \( y \): \[ y + 6 = 2x \implies y = 2x - 6 \]

Step 2: Substitute \( y \) into the First Equation

Substitute \( y = 2x - 6 \) into the first equation: \[ 9x - 3(2x - 6) = 12 \]

Simplify the equation: \[ 9x - 6x + 18 = 12 \implies 3x + 18 = 12 \]

Step 3: Solve for \( x \)

Solve the simplified equation for \( x \): \[ 3x + 18 = 12 \implies 3x = 12 - 18 \implies 3x = -6 \implies x = -2 \]

Step 4: Substitute \( x \) back into the Expression for \( y \)

Substitute \( x = -2 \) back into the expression \( y = 2x - 6 \): \[ y = 2(-2) - 6 = -4 - 6 = -10 \]

Final Answer

\(\boxed{(x, y) = \left(-2, -10\right)}\)

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