18. Use Structure Teresa placed parentheses in the expression below so that its value was greater than 80 . Write the expression to show where Teresa might have placed the parentheses. \( 10.5+9.5 \times 3-1 \times 2.5 \)

To make the value of the expression greater than 80, Teresa can strategically place parentheses to alter the order of operations, maximizing the result. Here's how she might do it: \[ (10.5 + 9.5) \times (3 - 1) \times 2.5 \] **Breakdown of the Calculation:** 1. **First Parentheses:** \((10.5 + 9.5) = 20\) 2. **Second Parentheses:** \((3 - 1) = 2\) 3. **Multiplication:** \(20 \times 2 = 40\) \(40 \times 2.5 = 100\) **Final Result:** \[ (10.5 + 9.5) \times (3 - 1) \times 2.5 = 100 \] This arrangement ensures that the expression evaluates to **100**, which is greater than 80.