9 + 13x = 35 + 26x
13x − 26x = 35 − 9
−13x = 26
$x = -\frac{26}{13}$
x = −2

$\frac{7}{9}x + 3 = \frac{2}{3}x + 5$
$\frac{7}{9}x - \frac{2}{3}x = 5 - 3$
$\frac{7}{9}x - \frac{6}{9}x = 2$
$\frac{1}{9}x = 2$
$x = 2 : \frac{1}{9}$
x = 2 * 9
x = 18

0,81x − 71 = 1,11x + 1
0,81x − 1,11x = 1 + 71
−0,3x = 72
$x = -\frac{72}{0,3}$
$x = -\frac{720}{3}$
x = −240

$\frac{1}{3}y - 4 = \frac{1}{4}y - 5$
$\frac{1}{3}y - \frac{1}{4}y = -5 + 4$
$\frac{4}{12}y - \frac{3}{12}y = -1$
$\frac{1}{12}y = -1$
$y = -1 : \frac{1}{12}$
x = −1 * 12
x = −12