The branch of mathematics in which we study the use of letters to write rules and formulae in a general way is known as _______.
Algebra
Algebra is the branch of mathematics in which we study the use of letters to represent numbers/quantities.
For example, ram bought mangoes, but we don't know the number of mangoes he bought. So, let's say he bought x number of mangoes.
Here x is an alphabet but represents the number of mangoes.