How do you solve by substitution $y – 3x = 7$ and $21 + 9x = 3y$ ?

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Answer 1 · 2018-03-09T14:06:03

$(x, y) = (x, 7 +3x)$

Equation 1: $y - 3x = 7=> y = 7 + 3x$

Substitution : Substitute 7 + 3x for y in the equation 2:

$21 + 9x = 3y$
$21 + 9x = 3(7 + 3x)$
$21 + 9x = 21 + 9x$
It is true for all real numbers => x can be any real number

$y = 7 + 3x$

Equation 1 and 2 are the same line, and the answers is $(x, 7 + 3x)$ .

How do you solve by substitution y – 3x = 7y – 3x = 7 and 21 + 9x = 3y21 + 9x = 3y?