Today is a delightful example of the spreadsheet method. The spreadsheet below is a peach of an example of this important Rashi method. The spreadsheet with its underlying assumptions justifies the Rashi assertion that The sale of the birthright, by Esauv, to Jacob, happened during the week of mourning for Grandpa Abraham's death.

'Egyptian Time*1	'Event	'Abraham's age	'Ishmael's age	'Isaac's age	'Jacob's / Esauv's age	'Joseph's age	'Jacob working for Laban	'Supporting Verses
' 0	'Abraham visits Egypt	'75	'	'	'	'	'	'Gn12-04
' 14	'Ishmael Born	'86	'0	'	'	'	'	'Gn16-16
' 25	'Isaac Born	'100	'	'0	'	'	'	'Gn21-05
' 85	'Yaakov Born	'	'	'60	'0	'	'	'Gn25-26
' 100	'Abraham's death	'175	'	'	'	'	'	'Gn25-07
' 100	'Esauv sells birthright to Jacob	'	'	'75	'15	'	'	'*2

Footnotes:
• 1: The 400 years of exile started in Abraham's 75th year and is numbered 0. The Jews left Egypt in year 405. This table links pairs of events with verses. The linked pairs justify an update of Egyptian time column. A bulleted summary of the spreadsheet is presented in the next footnote.
• 2 Here is a quick summary of the spreadsheet rows.
  • Abraham was 75 when he left his homeland and entered Egypt, Gn12-04. We refer to this as year 0 of the Egyptian exile since it is the first time a Jew entered Egypt.
  • Abraham was 86 when Ishmael was born, Gn16-16. Hence Ishmael's birth happened in year 86-75=11, Egyptian time.
  • Abraham was 100 when Isaac was born, Gn21-05
  • Isaac was 60 when Jacob and Esauv were born, Gn25-26
  • Hence Abraham was 100+60=160 when Jacob and Esauv was born
  • Abraham was 175 at death, Gn25-07
  • Hence Jacob and Esauv were 15 at Abraham's death.

Now we can discuss the Rashi. Gn25-30 discusses the sale of the birthright by Esauv to Jacob. But no age is listed. We know, as discussed in rule #7 above, that intentionally red vegetables were being cooked by Jacob but we don't know why they were intentionally red. One reasonable assumption is that the intentionally red vegetables were being cooked as a symbol of mourning (See rule #10 below). Using that reasonable assumption we check and find that Abraham died at 175 when Jacob and Esauv was 15. The discussion presented in the Biblical text: " Jacob: I would like your birthright. Esauv: I lead a physical life and don't really need the birthright-priesthood, is the type of discussion that teenagers have about their aspirations in life.

Nothing has been proven. But the spreadsheet makes it apear emminently reasonable that the sale happened during the week of mourning for Abraham. This example illustrates the flavor of the spreadsheet method. It shows what Rashi does as well as what he does not do. It also instructs on the proper attitude towards Rashi.