The Occupational Safety and health Administration (OSHA) estblished permissible sound exposures in the work-place. This is modeled by the equation: S=-2.817H + 108.9
Use the formula for the problem:
S=maximun permissible sound level in decibels
H=number of hours of exposure
How long can you be exposed to receive a maximum sound level of 105 decibels?
Assuming your formula is correct, substitute 105 for S and solve for H.
I hope this helps. Thanks for asking.