Consider that a retired couple has $240,000 to invest. They chose one relatively safe investment fund that has an annual yield of 8% and another riskier investment that has a 12% annual yield.

Let us find how much they should invest in each fund to earn $23,200 per year.

Denote the fund invested at 8% as x and the fund invested at 12% as y.

Then we have the equation

...... (1)