Question

How many pounds of nuts worth $1.05 a pound must be mixed with nuts worth $0.85 a pound to get a mixture of 200 pounds of nuts worth $0.90 a pound?

Answer 1

If x=number of pounds of nut worth $1.05/pound and y=number of pounds of nuts worth $0.85/pound, we know two things.

x+y=200
1.05x + 0.85y =200 (0.9)

solve equation 1 for x=200-y, substitute into the 2nd equation and you have your answer.