I am in a discrete mathematics class for information technology. I need some help setting up the equation(s) for a particular problem. It has been difficult to get individual attention with my rather large class size. I'm hoping to find just a little help here :)
Ok, so supposing that I invest \$20,000 into two accounts, paying 7% and 9% annual interest, respectively. If the total interest earned for the year is \$1550, how much was invested at each rate?
Let $x$ be the amount of money invested into the $7\%$ account and let %y% be the amount of money invested into the $9\%$ account. We know that $x+y=20000$ (the total amount of money) and that $0.07\cdot x+0.09\cdot y=1550$, because that's how much interest was earned. I'm sure you can solve it from here.