According to a survey of American households, the probability that the residents own 2 cars if annual household income is over $25,000 is 80%. Of the households surveyed, 60% had incomes over $25,000 and 70% had 2 cars. The probability that the residents of a household own 2 cars and have an income over $25,000 a year is:

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.