(Solve by the cramer method) An investor tells his broker that all his shares are in three companies Delta, Hilton and McDonald's and that two days ago his value fell $ 350 but yesterday it increased $ 600. The broker recalls that two days ago Delta shares fell $ 1 per share and Hilton's $ 1.50, but that the price of McDonalds shares rose $ 0.50. He also remembers that yesterday Delta's stock price rose $ 1.50 per share, Hilton's share fell another $ 0.5 per share and McDonald's rose $ 1.0 per share. He shows that the broker does not have enough information to calculate the number of shares the investor owns in each company, but that if he says that he has 200 shares in McDonald's, the broker can calculate the number of shares that he has in Delta and Hilton.