The Years of Moses

It is alleged that there is in Acts 7:23, 30, 36, the distinct mention of three periods of forty years, of which only the last is mentioned in the Pentateuch. But if we turn to Ex. 7, we are told that “Moses was fourscore years old . . . when they spake unto Pharaoh” v. 7). Now these fourscore years of Moses exactly agree with Stephen’s account, that he was forty years old when it came into his heart to visit his brethren the children of Israel, and was forty years after in Madian. This also fits in perfectly with Ex. 2:11, 15, and 7:7. Stephen makes the age of Moses to be one hundred and twenty years altogether; and in Deut. 22:2, and 34:7, he is said to have died at the age of one hundred and twenty years. Now, where is there any discrepancy?