6. Integers
7. Fractions
8. Decimals
10. Mensuration
11. Algebra
11.1. Algebraic Expressions
11.1.2. Variables and Constants
11.1.4. Types of Algebraic Expressions
11.1.6.1. Addition of Algebraic Expressions
11.1.6.2. Subtraction of Algebraic Expressions
13. Symmetry