Пошаговое объяснение:

[tex] {3}^{x} + {3}^{x + 2} > 90 \\ {3}^{x} + {3}^{x} \times {3}^{ 2} > {3}^{2} \times 10 \\ {3}^{x} (1 + {3}^{2} ) > {3}^{2} \times 10 \\ {3}^{x} (1 + 9) > {3}^{2} \times 10 \\ {3}^{x} \times 10 > {3}^{2} \times 10 \\ {3}^{x} > {3}^{2} \\ x > 2[/tex]