Lech Lecha: Yitzchak and Yaakov

Yishmael was 14 years old when Yitzchak  was born [Bereishis  17:25, 18:10]. Yaakov  was born to Yitzchak when Yitzchak was 60 years old [Bereishis 25:26].

Question: How old was Yitzchak when Yaakov was born?

Answer: 14 + 60 = 74 years