THERE IS A TOTAL OF 240*.03=7.2 GALLONS OF SALT IN THE 240 GALLONS.
TO GET A 5% SOLUTION YOU MUST DRAIN ENOUGH TO GET LEAVE THE FOLLOWING
.05X=7.2
X=7.2/.05
X=144 GALLONS OF WASTER WITH 7.2 GALLONS OF SALT IS A 5% SOLUTION.
THEREFORE YOU MUST EVAPORATE
240-144=96 GALLONS OF WATER.