This Bible contradiction is from the Skeptic's Annotated Bible.
75 years old
Genesis 12:4 View context
Abram [Abraham] was seventy and five years old when he departed out of Haran.
At least 135 years old
Genesis 11:26-32 View context
Abraham's father, Terah, was 70 years old when Abram was born.
And Terah lived seventy years, and begat Abram [Abraham].
Acts 7:2-4 View context
Abraham didn't leave Haran until after Terah died.
Our father Abraham ... dwelt in Haran: and from thence, when his father was dead, he removed himself into this land.
Genesis 11:32 View context
And Terah lived to be 205.
And the days of Terah were two hundred and five years; and Terah died in Haran.
So Abraham was at least 135 years old when he left Haran.