Question

you have two saltwater solutions.one consists of 20% salt, and the other consists of 15% salt.

A.if you want to add these two together to make 5 gallons of a 17% solution, how much solution should you add?

Answer 1

Answer: 2 gallons of the .2 salt solution and 3 gallons of the .15 salt soln.

This problem is basically about setting up a system of equations.
So what you get is these two equations based on the info you're given:
.2x + .15y = .17(5) <--- Think of this as "this amount of salt" + "this amount of salt" = "that amount of salt."
x + y = 5 < --- Think of this as "this many gallons of water" + "this many gallons of water" = "that many gallons of water."

Then you just solve the system for x & y.

Answer 2

if you wanted to make 5 gallons of a 19% solution, what volume of each solution should you add?

Answer 3

4 gal. of the .2 soln. and 1 gal. of the .15 soln. All you do is change .17(5) to .19(5) in the 1st equation and solve for the system again.