It was already there ”in the mixture. 
It was already contained in the mixture.
It was not already a part of the mixture
A teacher is reading to a classroom.
The Medicare Trustees' estimates were made in 1998.
The people are running outside in a race.
Laurence Benaam writes regularly in Le Monde.
Kids are playing with squirt guns.
He rarely show up at the Dallas scene, so no one knows anything about him.