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?

36 gallons of water need to be evaporated.

Step-by-step explanation:

Let x gallons be the amount of water needed to be evaporated. Then (90 - x) gallons of solution will left.

1. Calculate the amount of salt in 90 gallons of a 15% salt solution:

2. Calculate the amount of salt in (90 - x) gallons of a 25% salt solution:

3. The amount of salt remains unchanged, so

4. Solve this equation:

36 gallons of water need to be evaporated.

the answer to your question is b.