Question 1081639
Eight gallons of salt consists of 35% salt.
 It is the result of mixing a 50% solution with a 30% solution.
 How many gallons of each of the solutions was used?
 The corresponding modeling system is 
 X + y = 8
.5x+.3y=.35(8)
:
 X + y = 8
.5x+.3y= 2.8
multiply by 2, subtract from the 1st equation
x + y = 8
x +.6y = 5.6
---------------Subtraction eliminates x find y
0 + .4y = 2.4
y = 2.4/.4
y = 6 gallons of 30% solution
then
x = 2 gallons of 50% solution