Original: Margaret Hilda Thatcher , Baroness Thatcher LG , OM , PC , FRS ( born 13 October 1925 ) served as Prime Minister of the United Kingdom from 1979 to 1990 and Leader of the Conservative Party from 1975 to 1990 .
Simplified: Margaret Hilda Thatcher , Baroness Thatcher LG , OM , PC , FRS ( born Margaret Hilda Roberts October 13 , 1925 ) was the first woman Prime Minister of the United Kingdom from 1979 to 1990 .