a)
[tex] \frac{x - 3}{x + 7} = \frac{2}{5} \\ x - 3 = \frac{2 \times (x + 7)}{5} \\ 5(x - 3) = 2x + 14 \\ 5x - 15 = 2x + 14 \\ 3x = 29 \\ x = \frac{29}{3} = 9 \frac{2}{3} [/tex]
b)
[tex] \frac{ {x}^{2} - 9}{2x - 6} = 0 \\ \\ x≠3 \\ \\ {x}^{2} - 9 = 0 \\ {x}^{2} = 9 \\ x = - 3[/tex]
