Math
posted by Drew .
Althea invested $10,000 for one year, part at 7% and part at 6 1/4%. If she earned a total interest of
$656.50, how much was invested at each rate?

x = amount at 7%
y = amount at 6.25%
x + y = 10,000 or x = 10,000  y
.07x + .0625y = 656.50
You can solve by substitution:
.07(10,000  y) +.0625y = 656.50