Solve by Substitution x+y=3 , x-y=9

$x + y = 3$ , $x - y = 9$

Step 1

Subtract $y$ from both sides of the equation.

$x = 3 - y$

$x - y = 9$

Step 2

Replace all occurrences of $x$ with $3 - y$ in each equation.

Replace all occurrences of $x$ in $x - y = 9$ with $3 - y$ .

$(3 - y) - y = 9$

$x = 3 - y$

Simplify the left side.

Subtract $y$ from $- y$ .

$3 - 2 y = 9$

$x = 3 - y$

$3 - 2 y = 9$

$x = 3 - y$

$3 - 2 y = 9$

$x = 3 - y$

Step 3

Solve for $y$ in $3 - 2 y = 9$ .

Move all terms not containing $y$ to the right side of the equation.

Subtract $3$ from both sides of the equation.

$- 2 y = 9 - 3$

$x = 3 - y$

Subtract $3$ from $9$ .

$- 2 y = 6$

$x = 3 - y$

$- 2 y = 6$

$x = 3 - y$

Divide each term in $- 2 y = 6$ by $- 2$ and simplify.

Divide each term in $- 2 y = 6$ by $- 2$ .

$\frac{- 2 y}{- 2} = \frac{6}{- 2}$

$x = 3 - y$

Simplify the left side.

Cancel the common factor of $- 2$ .

Cancel the common factor.

$\frac{- 2 y}{- 2} = \frac{6}{- 2}$

$x = 3 - y$

Divide $y$ by $1$ .

$y = \frac{6}{- 2}$

$x = 3 - y$

$y = \frac{6}{- 2}$

$x = 3 - y$

$y = \frac{6}{- 2}$

$x = 3 - y$

Simplify the right side.

Divide $6$ by $- 2$ .

$y = - 3$

$x = 3 - y$

$y = - 3$

$x = 3 - y$

$y = - 3$

$x = 3 - y$

$y = - 3$

$x = 3 - y$

Step 4

Replace all occurrences of $y$ with $- 3$ in each equation.

Replace all occurrences of $y$ in $x = 3 - y$ with $- 3$ .

$x = 3 - (- 3)$

$y = - 3$

Simplify the right side.

Simplify $3 - (- 3)$ .

Multiply $- 1$ by $- 3$ .

$x = 3 + 3$

$y = - 3$

Add $3$ and $3$ .

$x = 6$

$y = - 3$

$x = 6$

$y = - 3$

$x = 6$

$y = - 3$

$x = 6$

$y = - 3$

Step 5

The solution to the system is the complete set of ordered pairs that are valid solutions.

$(6, - 3)$

Step 6

The result can be shown in multiple forms.

Point Form:

$(6, - 3)$

Equation Form:

$x = 6, y = - 3$

Step 7

Solve by Substitution x+y=3 , x-y=9

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