Answer
$2511.9$
Work Step by Step
We know that $M=\log\frac{I}{S}$ and thus $10^M=\frac{I}{S}$
Hence, here if $I_1,I_2$ are the intensities, we have:
$I_1=S10^{8.3},I_2=S10^{4.9}$
Hence,
$\frac{I_1}{I_2}=\frac{10^{8.3}}{10^{4.9}}\approx2511.9$
