Otto has some whipping cream that is 30%, percent butterfat and some milk that is 2%, percent butterfat. He wants to make a 500\,\text{mL}500mL500, start text, m, L, end text mixture of them that is 12\%12%12, percent butterfat. Here's a graph that shows a system of equations for this scenario where xxx is the volume of whipping cream he uses and yyy is the volume of milk he uses.