That is exactly what you are given! For example,

Find A- B.b) Find a matrix C reflecting the change in the stock portfolios of Adam and Bob between the end of September and the end of October.]

Set up the column matrix and multiply BV.c) If the prices (in dollars per share) of stocks IBM, GE, and Walmart at the close of the stock market on October 31 were $110, $50, and $60, respectively, use the matrix operation to find the values of the portfolios of Adam and Bob in the form of a matrix.