Final answer:
Benjamin Banneker sent a copy of his book to Thomas Jefferson, the third President of the United States.
Step-by-step explanation:
Benjamin Banneker sent a copy of his book to Thomas Jefferson, who was the third President of the United States. Banneker's book was a mathematical treatise called 'Benjamin Banneker's Pennsylvania, Delaware, Maryland, and Virginia Almanack and Ephemeris,' which included calculations for predicting solar and lunar eclipses. Banneker sent the book to Jefferson in 1791, along with a letter expressing his views on racial equality and his hope for the abolition of slavery.