Question 852413
Amount of salt will be the same before and after evaporation.

Amount of salt is 16*(0.02).


Amount of salt solution at the beginning is 16 ounces.  Most of this is water, and some of it is salt.  The WATER WILL DECREASE THROUGH EVAPORATION.  


At start, fraction of the solution being salt is {{{(16(0.02))/16=0.02}}}.


After the needed evaporation, the numerator is unchanged, but the denominator must be decreased; and the resulting fraction must equal 0.04.


From that, do you know what to do?