Genesis 11:26 And Terah lived seventy years, and begat Abram, Nahor, and Haran. (KJV)
Genesis 11:32 And the days of Terah were two hundred and five years: and Terah died in Haran. (KJV)
Genesis 12:1 Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father's house, unto a land that I will shew thee: (KJV)
Genesis 12:4 So Abram departed, as the LORD had spoken unto him; and Lot went with him: and Abram was seventy and five years old when he departed out of Haran. (KJV)
Note: The assumption of an inconsistency is that Terah was 70 when Abraham was born, and then died at the age of 205, and then the Bible says that Abraham was 75 upon the death of Terah, when Abraham really would have been 135.
It's unlikely that Abraham, Nahor, and Haran were triplets, so they were probably not all born in the 70th year. The 70th year was the year that Terah began having children. Orders listed in a single passage does not necessarily reflect birth order (for example, Noah's children are listed in Genesis 5:32 as Shem, Ham and Japheth, though Japheth is the oldest and Ham the youngest). Most scholars think that Abraham was the youngest of his three brothers, so Abraham could have been born in the 130th year, thus making him 75 when Terah died. Not a contradiction.