How many milligrams of drug are in 45 ml of a 1.5% w/v solution?

 The  number  of  milligrams  of drug   that are  in 45 ml  of a 1.5%  w/v   solution
is 0.675   mg

           calculation
 this is calculated using  ( %M/V =  mass  in milligrams/   volume  x100    formula )

%M/V  = 1.5 %
volume  = 45 ml
mass = ?

convert  %(m//v)  into  fraction  = 1.5/100    and let  the mass be represented by  y

 therefore  1.5/100  =     y/45

cross  multiplication

=67.5 =  100 y

divide both  side by  100

y=0.675  mg

Not a  mixture of two common elements that can be separated by physical means.