I just started learning about matrices in class, so this question is supposed to be fairly simple.. but I've never been any good at math, so I'm having a bit of trouble with it.

Mark had $24,500 to invest. He divided the money into three different accounts. At the end of the year, he had made $1,300 in interest. The annual yield on each of the three accounts was 4%, 5.5%, and 6%. If the amount of money in the 4% account was four times the amount of money in the 5.5% account, how much had he placed in each account?

I started with -

0.06 0.055 0.04 1300

1 1 1 24500

0 422 -104 0

then I stopped at

0 1 4 34000

1 0 -4 -9500

0 0 792 7174000

I'm stuck!!