After Willy hears Biff's news about Bill Oliver, what flashback occurs?

After Biff tells Willy Loman about the disastrous attempt
to meet with Bill Oliver, Willy reverted back to when Biff was younger, and had flunked
Math, hence losing the few extra points he needed to enter the University of Virginia.
During this argument, he also reverts to when Linda told him that Biff went to see Willy
at his hotel, and how Biff found out about the mistress that was with his father at the
hotel. Willy also remembered in a flash how Biff cried, how he promised him that he
would go see the teacher, and how everything will be OK. Yet, out of all this, the first
memory was flunking Math because, had Biff not flunked (according to Willy), his life
would have been "set".