Question

solving systems by substitution
example 1 (equal values method)
solve: $y=2x$
$y=9-x$
since $y$ represents equal values in both equations, we can write $2x=9-x$.
solving for $x$: $2x=9-x$
$+x$ $+x$
$3x=9$
$x=3$

Explanation:

Step1: Set equations equal

$2x = 9 - x$

Step2: Add x to both sides

$2x + x = 9 - x + x$
$3x = 9$

Step3: Divide by 3

$x = \frac{9}{3}$

Step4: Find y using x=3

$y = 2(3)$

Answer:

$x=3$, $y=6$