Otto has some whipping cream that is 30% butterfat and some milk that is 2% butterfat. He wants to make a 500 mL mixture of them that is 12% butterfat.
Here's a graph that shows a system of equations for this scenario where x is the volume of whipping cream he
uses and y is the volume of milk he uses.

THE ANSWER IS A: The mixture has the intended volume and has the intended percent of butterfat.

YA WELCOME LESBIANS ;)