Question

2 when solving the given system of linear equations by using the substitution method, which equation could be used?
$x - 3y = 9$
$4x + 2y = 7$
a $y = 9 - 3x$
b $y = 7 - 4x$
c $x = 7 + 4y$
d $x = 9 + 3y$

Explanation:

Step1: Isolate x in first equation

$x - 3y = 9 \implies x = 9 + 3y$

Step2: Isolate y in first equation

$x - 3y = 9 \implies -3y = 9 - x \implies y = \frac{x - 9}{3}$

Step3: Isolate y in second equation

$4x + 2y = 7 \implies 2y = 7 - 4x \implies y = \frac{7 - 4x}{2}$

Step4: Isolate x in second equation

$4x + 2y = 7 \implies 4x = 7 - 2y \implies x = \frac{7 - 2y}{4}$

Step5: Match with options

Compare derived equations to given choices.

Answer:

D. $x = 9 + 3y$