The expression "b + a" represents the addition of two variables, b and a. In mathematics, addition is a fundamental operation that combines quantities. The result of this operation is called the sum. The order of addition does not affect the outcome, meaning that b + a is the same as a + b. In various contexts, b and a can represent different values or objects. For example, in a simple equation, b could be 3 and a could be 5, making b + a equal to 8. This concept is widely used in algebra, finance, and everyday calculations.