I = 7.6*10^(-4) is the given intensity of the sound
Io = 10^(-12), which is a constant usually shown in a table or in your book
Plug in those values to get
B = 10*log(I/Io)
B = 10*log((7.6*10^(-4))/(10^(-12)))
B = 88.808135922808
B = 88.81
Answer: Approximately 88.81 decibels