A total of 15,000 is invested in two accounts. One of the accounts earns 12% per year, and the other earns 10% per year. If the total interest earned in the first year is 1,600 how much was invested in each account?

Let h represent the amount invested at the high interest rate. The equation for the total income is
  12%*h + 10%*(15000 - h) = 1600
  2%*h + 1500 = 1600    (use the distributive property and collect terms)
  2%*h = 100    (subtract 1500)
  h = 5000    (multiply by 50)

$5,000 was invested at 12% and $10,000 was invested at 10%.