Carlon plans to evaporate a number of gallons of water from 90 gallons of a 15% salt solution to make a 25% salt solution. Which equation can he use to find x, the number of gallons that should be evaporated?
the options are
1. 13.5/90-x = 25/100
2. 13.5/x =25/100
3. 13.5(90-x) = 0.25
4. 13.5(90-x) = 25