An individual is legally intoxicated with a blood alcohol level of 0.08% (w/v) of ethanol.

We have a couple of problems with this problem. First, w/v means weight per volume and milligrams is a measure of mass, not weight, but legal eagles are probably too stupid to know that. For instance the law specifies blood alcohol content, but the instrument used to obtain evidence measures breath alcohol content, which is only vaguely related. So the instrument's programming must contain an assumption about converting one figure to the other. For that reason a lawyer will subpoena the programming of the instrument. Of course the manufacturer will refuse to reveal the programming, so the case has to be thrown out for lack of evidence.

Second, no info is given to determine the correct number of significant figures.

So what exactly are we supposed to do with this?