92
Jackson played 26 games in the Spanish league last season and scored 12 goals, including nine in the last eight rounds. He made his debut for Senegal at the World Cup in Qatar in December.
He is the second summer signing for Chelsea after the arrival of Christopher Nkunku from Leipzig. In the new season, the Blues will try to make up for the 12th place from last year, which was their worst position since 1994. The team will be led by new coach Mauricio Pochettino.