The following equation is incorrect due to two operator signs being placed wrongly. Which two signs should be interchanged (swapped wherever they appear) to make the equation correct? 18 - 2 ÷ 20 + 5 x 16 = 69

Introduction / Context:This question tests operator-interchange correction. You must identify which two operators, when swapped throughout the expression, make the left-hand side equal the right-hand side. The challenge is systematic checking while respecting arithmetic precedence.

Given Data / Assumptions:

• Equation: 18 - 2 ÷ 20 + 5 x 16 = 69
• Exactly two operator signs must be interchanged.
• After swapping, evaluate using standard precedence: division and multiplication before addition and subtraction.

Concept / Approach:Try each suggested pair-swap by replacing every occurrence of the first sign with the second and vice versa. Then compute the new left-hand side. The correct swap is the one that yields 69.

Step-by-Step Solution: Test option: swap ÷ and -. Original: 18 - 2 ÷ 20 + 5 x 16 After swapping ÷ and -: 18 ÷ 2 - 20 + 5 x 16 Now evaluate: 18 ÷ 2 = 9 5 x 16 = 80 So LHS = 9 - 20 + 80 9 - 20 = -11 -11 + 80 = 69 This matches RHS = 69.

Verification / Alternative check:Because the final computed value matches exactly, no further swaps are required. Also, the structure is sensible: a clean division at the start, then addition of a large product, which naturally can reach 69.

Why Other Options Are Wrong: + and x: changes only one multiplication location and typically produces non-69 values. + and ÷: creates multiple divisions/additions that shift the result far from 69. - and +: mostly rearranges plus/minus but keeps 2 ÷ 20 small, not enough adjustment. x and ÷: disrupts the big 5 x 16 term, making it hard to reach 69.

Common Pitfalls:Swapping only one occurrence of a sign, ignoring precedence, or doing swaps mentally without rewriting often leads to wrong conclusions.

Final Answer:÷ and -