(5x + 1)(2x − 3) = (10x − 9)(x + 2)
$10x^2 + 2x - 15x - 3 = 10x^2 - 9x + 20x - 18$
$10x^2 - 10x^2 + 2x - 15x + 9x - 20x = -18 + 3$
−24x = −15
$x = \frac{15}{24} = \frac{5}{8}$

(7x − 1)(x + 5) = (3 + 7x)(x + 3)
$7x^2 - x + 35x - 5 = 3x + 7x^2 + 9 + 21x$
$7x^2 - 7x^2 - x + 35x - 3x - 21x = 9 + 5$
10x = 14
x = 14 : 10
x = 1,4