Let the weights of the cashews and almonds be c and a respectively.
Then ($8)c + ($6)a = $48. Note that c + a = 7 lb, so that c = 7 lb - a.
Then 8(7-a) + 6a = 48, and 56 - 8a + 6a = 48.
Solving for a: 8 = 2a, and a = 4 lb. Then c = 7 lb - 4 lb = 3 lb.
3 lb of cashews and 4 lb of almonds (answer)