How many gallons of a 10% salt solution must be mixed with 20 gallons of a 25% salt solution to produce a 20% salt solution? (Let "x" represent the total number of gallons in the container of 10% solution. Therefore, 20+x will represent the total number of gallons in the final container of 20% solution)
a.) Write an algebraic equation for this problem
b.) Solve the equation for the number of gallons needed (x)