Mixture of Nuts and Investments

I would like some help on these problems.

The Quik Mart has two kinds of nuts. Pecans sell for $1.55 per pound and walnuts sell for $1.95 per pound. How many pounds of walnuts must be added to 15 pounds of pecans to make a mixture that sells for $1.75 per pound?

I came up with the equation:

23.25 + 1.95x = 1.75 (x + 15)

And got I got x to be 2.5, so I think I need 2.5 pounds of walnuts.

And on this problem I'm immensely confounded, A push in the right direction is vitally needed:

Alice Gleason invested a portion of $32,000 at 9% interest and the balance at 11% interest. How much did she invest at each rate if her total income from both investments are $3,200?