Question 442804
Let x= # of ounces of 30% solution
    x+50= # of ounces of 20% saline solution
.3(x)+.12(50)=.2(x+50)
.3(x)+6=.2x+10
-.2x -6 -.2x -6
[.1x=4]*10
1x=40
x=40

Check
40(.3)+50(.12)=90(.2)
12+6=18
18=18
Correct

Answer: 40 ounces of a 30% solution must be added