1/(x - 6) + 4/(x + 6) = 3/(x - 4)
( x + 6 + 4x - 24)/(x - 6)(x + 6) = 3/(x - 4)
(5x - 18)/(x² - 36) = 3/(x - 4)
3(x² - 36) = (x - 4)(5x - 18)
3x² - 108 = 5x² - 38x + 72
3x² - 5x² + 38x - 180 =0
- 2x² + 38x - 180 = 0
2x² - 38x + 180 = 0
x² - 19x + 90 = 0
D = b² - 4ac = 361 - 360 = 1
x1 = ( 19 + 1) / 2 = 10
x2 = ( 19 - 1) / 2 = 9