[tex] \frac{2x - 8}{3x - 12} = \frac{2(x - 4)}{3(x - 4)} = \frac{2}{3} [/tex]
[tex] \frac{5x - 15}{ {x}^{2} - 9 } = \frac{5(x - 3)}{(x - 3) \times (x + 3)} = \frac{5}{x + 3} [/tex]
[tex] \frac{ {x}^{2} - 9}{ {x}^{2} - 6x + 9 } = \frac{(x - 3) \times (x + 3)}{(x - 3) {}^{2} } = \frac{x + 3}{x - 3} [/tex]
[tex] \frac{x {}^{2} - 10x + 21 }{x {}^{2} - 9 } = \frac{x { }^{2} - 3x - 7x + 21}{(x - 3)(x + 3)} = \frac{x \times (x - 3) - 7(x - 3)}{(x - 3)(x + 3)} = \frac{(x - 3)(x - 7)}{(x - 3)(x + 3)} = \frac{x - 7}{x + 3} [/tex]
