I would love to help! However I'm not sure what I'm supposed to be helping with. I could just be daft, but it isn't clear what you need from me.
First we need to write the equations for the given scenario. Using the equations, we can form a system of matrix for the situation.
Let the customer buys, x pounds of almonds, y pounds of cashews and z pounds of walnuts. Since he buys 12 pounds of mixed nuts, we can write:
Total cost of these mixed nuts was $118. So we can write:

Customer buys 2 more pounds of walnut than cashews. So, we can write:

Using these equations, we can set up the system of matrix as shown below in the image.
Answer:
68 miles per hour
Step-by-step explanation:
Divide 612 miles by 9 hours