Final answer:
To determine how many of each ingredient to buy, we can set up a system of equations. Solving the system, we find that you should buy 0 pounds of almonds and hazelnuts, and 9 pounds of raisins.
Step-by-step explanation:
To determine how many of each ingredient you should buy, let's set up a system of equations. Let's say you need x pounds of almonds, y pounds of hazelnuts, and z pounds of raisins. According to the problem, you want the mix to contain an equal amount of almonds and hazelnuts, so x = y. You also want the nuts to be twice as much as the raisins, so x + y = 2z. Lastly, you want to fill nine 1-lb tins, so x + y + z = 9.
You now have a system of three equations with three variables:
x = y
x + y = 2z
x + y + z = 9
Since x = y, we can substitute y with x in the second and third equations:
x + x = 2z
2x + z = 9
We can solve this system of equations:
Subtracting the first equation from the second equation, we get:
2x + z - (x + x) = 9
2x + z - 2x = 9
z = 9
Substituting z = 9 back into the second equation, we get:
2x + 9 = 9
2x = 0
x = 0
Since x = y, y = 0 as well.
So, you should buy 0 pounds of almonds and 0 pounds of hazelnuts. However, since you want the mix to contain nuts, you should buy some raisins. Since the ratio of nuts to raisins is 2:1, you can buy 9 pounds of raisins.