Shawn Hetrick has an annual interest income of $3290 from two investments. He has $7000 more invested at 8% than he has invested at 6%. find the amount invested at each rate.

Can anyone solve this for me? I'm a bit confused.. Well not really, more like I'm stuck. The problem I have is that this question doesn't give to total he invested on the 8% and 6%. I just can't think of an equation for this.