On  the  decibel  scale,  a  “quiet  whisper  1  meter  away”  is  about    decibels,  where  a  “jackhammer  3  meters  away”  is    decibels.  a) 20,  100      b)  10,  100      c)  10‐15,  90 

Looking at decibel scale tables on internet, a "quiet whisper 1 meter away" is generally reported to have a sound intensity of about 20 dB, while a jackhammer 3 meters away produces a sound of about 100 dB of intensity, so option a) could be the correct one.
However, the other options could be considered correct as well, because without knowing the exact sound power produced by the whisper or by the jackhammer it's impossible to calculate the exact sound intensity with precision, and since the values reported in the three options are very similar, all the three of them can be considered as valid.

By dividing you can find the answer

Wish i knew this to !