In Death of a Salesman, why does Biff's effort to tell Willy about meeting Oliver trigger Willy's memories of Biff's failing math?
Throughout his life, Willy has enabled Biff, never holding him accountable for his actions and never taking responsibility as a parent for his son's character development. When Willy demands to know how Biff's meeting went with Bill Oliver, he wants to hear only what he wants to hear--that Biff has been successful. He pushes Biff, giving him little chance to speak. When Biff becomes frustrated and angry because his father isn't listening to what he needs to say, Willy becomes accusatory. Once again he is faced with Biff's failure, and it is a reality he can't stand to face.
This throws him back into the memory of another instance of Biff's failing. Willy relives the day Young Bernard brings the news to Linda that Biff has failed math, will not graduate, and will not be going to college. When Willy returns to the present, he tells Biff, "Don't blame everything on me! I didn't flunk math--you did!" Willy refuses to accept responsibility for his son's lack of success in life, but there is another responsibility he avoids. If Biff had not failed math, he would not have gone to Boston to find Willy in the hotel room with another woman. Willy was prepared to save Biff's grade just before the woman was discovered in the room, breaking his son's heart. The grade was not saved. Biff was lost to Willy.