NCERT Class 6 Mathematics Textbook for Blind Students made Screen Readable by Professor T K Bansal.

Our studies so far have been with numbers and shapes. We have learnt numbers, operations on numbers and properties of numbers. We applied our knowledge of numbers to various problems in our daily life. The branch of mathematics in which we studied numbers is known as arithmetics. We have also learnt about figures in two and three dimensions and their properties. The branch of mathematics in which we studied shapes is known as geometry. Now we begin the study of another branch of mathematics. It is called algebra.

The main feature of this new branch which we are going to study in this chapter is the use of letters. Use of letters will allow us to write rules and formulas in a general way. By using letters, we can talk about any number and not just a particular number.
Secondly, letters may stand for unknown quantities. By learning methods of determining unknown quantities, we develop powerful tools for solving puzzles and many problems from daily life.
Thirdly, since letters stand for numbers, arithematic operations can be performed on them as on numbers. This leads to the study of algebraic expressions and their properties.

You will find algebra interesting and useful. It is very useful in solving problems. Let us begin our study with simple examples.