The torah teaches us that when Binyomin was born to Yakov, his wife Rochel died. How old was Yakov Avinu when Rochel died and how many years was that before his petira?
Yaakov was 99 when Rachel died. He outlived her by 48 years.
The Talmud (Megilah 17a) says that Yaakov was away from his father for 36 years. The first 14 were at the Yeshiva of Ever, 20 were spent at Lavan's house, and the last two were spent along the way home (at Sukkos and Beis-El), after which Rachel died. Since Yosef was born six years before Yaakov left Lavan, Yosef was 8 years old when Rachel died.
Yosef was 30 when he stood before Pharaoh, and nine years later (seven of plenty and two of famine), Yaakov came to Egypt and was 130 years old. Yaakov died (or not) at the age of 147, seventeen years later, when Yosef was 56.
Thus, Yaakov outlived Rachel by 56 - 8 = 48 years.