Read Exodus 1
Joseph was thirty years old when pharaoh had his dreams and was made prime minister, he died at 110. His family was brought to Egypt around the third year of the famine so the people of Israel were in the land of Goshen around 75 years before Joseph died. They came as only 70 people but now they number so high that the Egyptians are afraid of them. So it's at this point that they are oppressed and enslaved by Pharaoh. I wonder what happened during those 75 years, and what happened in the next approximately 130 years. That's how long the people were in bondage to Egypt. The logic that Pharaoh uses to try and stifle the population by killing all of the male babies is pretty foolish. If the midwives comply, in a few years the workforce begins to make drastic changes. But note the idea of killing all of the male babies because the king is afraid, sounds like something a king in Jerusalem did a few centuries later.