Answer
$I=10^{-2.2}~W/m^2\approx 6.3\times10^{-3}~W/m^2$
Work Step by Step
We know that
$B=10\log\frac{I}{I_0}$
Hence, here we have
$\log I=\frac{B}{10}-12=\frac{98}{10}-12=9.8-12=-2.2$
Thus, we have the intensity
$I=10^{-2.2}~W/m^2\approx 6.3\times10^{-3}~W/m^2$