Simplify the following text for a Grade 10 native English-speaking person.
Original: Some examples of other well-known calculi are propositional calculus , variational calculus , lambda calculus , pi calculus , and join calculus .
Simplified: This main idea says that the two calculus processes , differential and integral calculus , are opposites . That is , a person can use differential calculus to undo an integral calculus process .