An executive invests $22,000, some at 8% and the rest at 6% annual interest. if he receives an annual return of $1,660, how much is invested at each rate?

Here's the equation I'm using:
0.08n + 0.06(22000-n) = 1660
Multiply both sides by 100:
8n + 132000-6n = 166000
Simplify:
2n + 132000 = 166000
Isolate n:
2n = 34000
n = 17000
8% invested: 17000
6% invested: 5000

The percent increase is 25%