A chemist mixed a solution which was 34% acid with another solution that was 18% acid to generate a 30-ounce solution which was 28% acid. How much of the 34% acid solution did he use?

Let x = the amount of 34% acid solution. Let y = the amount of 18% iodine solution. Because the total amount of solution was 30 oz., then x + y = 30. The amount of each type of solution added together and set equal to the amount of 28% solution could be expressed in the equation 0.34x + 0.18y = 0.28(30). Use both equations to solve for x. multiply the second equation by 100 to eliminate the decimal point: 34x + 18y = 28(30); simplify which equation: 34x + 22y = 840. Multiply the ?rst equation through 18:18x /16x = 18y /300 = 540. Add the two equations to eliminate y: 16x -0y = 300. Divide both sides of the equation by 16: 16x/16 , 300/16 =18.75. The amount of 34% acid solution is 18.75 ounces.