SOLUTION: How many ounces of 20% antifreeze solution must be mixed with 30 ounces of a 50% antifreeze solution to make a 40% antifreeze solution? I have no idea where to start on this. Pleas

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Think about this...You want to add x oz. of 20% AF solution to 30 oz. of 50% AF solution to make (30 + x) oz. of 40% AF solution.
You can set up the necessary equation from this description. But first, change the percents to their decimal equivalents. 20% = 0.2, 40% = 0.4, and 50% = 0.5
Simplify and solve for x.
Subtract 0.2x from both sides.
Now subtract 12 from both sides.
Finally, divide both sides by 0.2

You need to add 15 oz. of 20% AF solution to the 30 oz. of 50% AF solution to make 45 oz. of 40% AF solution.