How many pounds of mixed nuts that contain 70% peanuts must Shannon add to 15 pounds of mixed peanuts that contain 20% peanuts to make a mixture with 40% peanuts

10 pounds.

Step-by-step explanation:

Let x pounds be the amount of mixed nuts we require.

Amount of peanuts in this mix = 0.70x pounds. Amount of peanuts in the 20% mix = 0.20*15 = 3 pounds.

So we have the equation:-

0.70 x + 3 = 0.40 (x + 15)

0.70 x + 3 = 0.40 (x + 15)

0.70x + 3 = 0.40x + 6

0.70x - 0.40x = 6 - 3

0.30x = 3

x = 10.