Question

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?

Answer 1

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