Summary
Formula
A formula consists of constants and variables.
In a formula the variables are interrelated. A formula is an equation that establishes a relationship among the variables involved in it. The plural form of formula is formulae.
Framing a formula:
Expressing a given statement in the form of an equation by using variables and mathematical symbols is called framing a formula.
Subject of a formula:
The subject of a formula is a variable that is expressed in terms of the other variables.
In other words, in a formula, the variable standing alone on one side of the equality sign is called the subject of the formula. The subject of a formula always lies on left hand side of the equality sign. The coefficient of the subject is always one. The subject of a formula does not link with any other quantities.
Changing the subject of a formula:
Any one variable of a formula can be made the subject by transferring the variables.
Evaluation of the subject of a formula (substitution method):
Finding the value of the subject by substituting the values of the other variables is called the evaluation of the subject of a formula.
Steps to evaluate the subject of a formula:

Make the required variable the subject.

Substitute the values of the other variables in the formula.

Simplify the formula.