An investment club invested part of $8000 at 10% annual interest the rest at 12%. If the annual income from these investments is $900, how much was invested at each rate

Let x be the amount invested at 10%

so the amount invested at 12 % = (8000-x)

0.1x + 0.12 (8000-x) = 900

0.1x - 0.12x = 900 - 960

0.02x = 60

x = 3000 @ 10%

8000 - 3000 = 5000 @ 12%