1. **Problem statement:** Write an expression for the statement 'the sum of x and y divided by 2'. 2. **Understanding the problem:** The phrase "the sum of x and y divided by 2" can be interpreted in two ways because of ambiguity in the order of operations. 3. **Formula and explanation:** - If the sum of x and y is divided by 2, the expression is $$\frac{x + y}{2}$$. - If only y is divided by 2 and then added to x, the expression is $$x + \frac{y}{2}$$. 4. **Ambiguity explanation:** The statement is ambiguous because it is unclear whether the division by 2 applies to the entire sum $(x + y)$ or only to $y$. Without parentheses, the expression can be interpreted differently. 5. **Unambiguous statement for $\frac{a + b}{2}$:** "The average of a and b" or "The sum of a and b, all divided by 2". 6. **Final expressions:** - Ambiguous: "the sum of x and y divided by 2" could be either $$\frac{x + y}{2}$$ or $$x + \frac{y}{2}$$. - Unambiguous: $$(a + b) / 2$$ written as $$\frac{a + b}{2}$$.