Answers for a Jew
How many Jews went to Egypt with Jacob?
Question: Why does the New Testament mention 75 people who went to Egypt with Jacob, whereas the Old Testament talks about 70, who came to Egypt with Jacob?
Answer: Let us first read both passages from the Holy Scriptures.
«All the souls that came with Jacob into Egypt, which came out of his loins, besides Jacob's sons' wives, all the souls were threescore and six; And the sons of Joseph, which were born him in Egypt, were two [LXX: nine] souls: all the souls of the house of Jacob, which came into Egypt, were threescore and ten [LXX: seventy five]» (Gen 46:26-27).
«Then sent Joseph, and called his father Jacob to him, and all his kindred, threescore and fifteen  souls. So Jacob went down into Egypt, and died, he, and our fathers» (Act 7:14-15).
The Masoretic text of Gen 46:27 mentions 70 people, and the Septuagint (the Greek translation of the Old Testament) refers to 75. In this case, the Book of Acts in the New Testament follows the Septuagint.
How can you explain this discrepancy? Apparently, the Masoretic text adds Jacob, Joseph and his two sons, Manasseh and Ephraim to the 66 Jews that came to Egypt (66+4=70), whereas the Septuagint adds to them the sons of Manasseh and Ephraim – Joseph's "whole family" (see 1 Chron 7).
In any case, the number 75 originates in the Old Testament and is mentioned in the Septuagint written several centuries before Christianity.
(to be continued)