10. (b³)⁻⁴ / b⁻¹¹ при b=5;

1. b⁻¹² / b⁻¹¹ = b⁻¹²⁻⁽⁻¹¹⁾ = b⁻¹.

2. Substitute b=5: 5⁻¹ = 1/5.