(x + 1)/(2·x - 3) - (x - 2)/(4·x - 6) - (x + 6)/(20·x - 30) = 9/20
(x + 1)/(2·x - 3) - (x - 2)/(2·(2·x - 3)) - (x + 6)/(10·(2·x - 3)) = 9/20 | ·20·(2·x - 3)
20·(x + 1) - 10·(x - 2) - 2·(x + 6) = 9·(2·x - 3)
20·x + 20 - 10·x + 20 - 2·x - 12 = 18·x - 27
-10·x = -55
x = 5.5