15x + 12 = 9 + 3x
15x − 3x = 9 − 12
12x = −3
$x = -\frac{3}{12}$
$x = -\frac{1}{4}$

7 − 15y = 1 + 9y
−15y − 9y = 1 − 7
−24y = −6
$y = \frac{6}{24}$
$y = \frac{1}{4}$

8 + 16x = 5 − 2(x − 3)
8 + 16x = 5 − 2x + 6
16x + 2x = 5 + 6 − 8
18x = 11 − 8
18x = 3
$x = \frac{3}{18}$
$x = \frac{1}{6}$

28 − 19y = 34 + 5(8 − y)
28 − 19y = 34 + 40 − 5y
−19y + 5y = 74 − 28
−14y = 46
$y = -\frac{46}{14}$
$y = -\frac{23}{7} = -3\frac{2}{7}$