Final answer:
The black hand of the duplex air gauge indicates the pressure reading, but without more information, the question cannot be answered accurately.
Step-by-step explanation:
The black hand of the duplex air gauge indicates the pressure in the (26-100). The black hand on a gauge typically represents the pressure reading, while the red hand may represent the maximum pressure or a warning level. However, without additional context or information about the specific gauge being referred to, it is not possible to provide a more detailed answer.