Answer: 9 or 3
Step-by-step explanation:
[tex]3 {x}^{2} + 18x - 81 = 0 \\ \\ {x}^{2} + 6x - 27 = 0 \\ (x - 3)(x + 9) = 0 \\ x - 3 = 0 \: \: \: \: \: x + 9 = 0 \\ x = 3 \: \: \: \: x = - 9[/tex]
