Elementary Geometry for College Students (5th Edition)

$3x - 4y = 12$ $y = \frac{3}{4}x - 3$
$27x - 36y = 108$ 27, 36 and 108 are multiples of 9, so the whole equation can be divided by 9. $3x - 4y = 12$ $-4y = -3x + 12$ $y = \frac{3}{4}x - 3$