Question 1011699
(1)
w, amount of volume to evaporate for removal;
Amount of salt stays the same but amount of solution becomes less as result of removal of some w water.
{{{32*4/(32-w)=16}}}
-
{{{16(32-w)=32*4}}}
{{{16*32-16w=32*4}}}
{{{-16w=32*4-16*32}}}
{{{16w=16*32-32*4}}}
{{{w=32-2*4}}}
{{{highlight(w=24)}}}



(2) and (3), learn this:<a href="http://www.algebra.com/my/Two-Part-Mixture-with-one-material-quantity-unknown.lesson?content_action=show_dev">Two part mixture, one material quantity known, the other unknown</a>