The expression "(a + b)" represents the sum of two variables, a and b. In mathematics, variables are symbols used to represent numbers that can change or vary. This expression is fundamental in algebra and is often used to solve equations or to describe relationships between quantities. When you add a and b, you combine their values to find a total. For example, if a equals 3 and b equals 5, then "(a + b)" equals 8. This simple operation is essential in various fields, including science, engineering, and finance, where calculations are frequently required.