Solve the System of Equations x+y=4 y=-x+4

$x + y = 4$ $y = - x + 4$

Replace all occurrences of $y$ with $- x + 4$ in each equation.

Replace all occurrences of $y$ in $x + y = 4$ with $- x + 4$ .

$x - x + 4 = 4$

$y = - x + 4$

Simplify the left side.

Simplify $x - x + 4$ .

Remove parentheses.

$x - x + 4 = 4$

$y = - x + 4$

Subtract $x$ from $x$ .

$0 + 4 = 4$

$y = - x + 4$

Add $0$ and $4$ .

$4 = 4$

$y = - x + 4$

$4 = 4$

$y = - x + 4$

$4 = 4$

$y = - x + 4$

$4 = 4$

$y = - x + 4$

Remove any equations from the system that are always true.

$y = - x + 4$

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