What is the role of equations in this book?

In general equation is a statement of an equality containing one or more variables.solving the equation consists of determining which values of the variables make the equality true. Variables are also called unknowns and the values of the unknowns which satisfy the equality are called solution of the equation. For example Ax + Bx + c = y. In this equation x and y are variables and A,B and C are parameters. Or Equation will derived to make understand the...