1. The problem is to understand why there are 3 brackets in the expression or context you are referring to. 2. Brackets are used in mathematics and programming to group terms, clarify order of operations, or denote function arguments. 3. Three brackets might appear if there are nested groupings, for example: $$((a+b)+c)$$ or in programming syntax like function calls within function calls. 4. Each pair of brackets serves to separate or prioritize parts of an expression. 5. Without a specific example, the general reason for 3 brackets is to indicate nested grouping or multiple levels of operations. 6. If you provide the exact expression, I can explain the role of each bracket in detail.