Fill the four operator slots (in order) with one of the given sign sequences, placing an “=” in exactly one slot, so the statement balances: 2 * 4 * 3 * 4 * 9 Choose the correct ordered replacement (left→right).

Difficulty: Medium

Correct Answer: x - + =

Explanation:


Introduction / Context:
We must replace the four “*” slots (between the five numbers) with the four signs from exactly one option, in that order, with one of the slots being an equals sign. Standard operator precedence (×, ÷ before +, −) applies on each side of “=”.


Given Data / Assumptions:

  • Numbers: 2 • 4 • 3 • 4 • 9 (four slots)
  • Each option gives a left→right sequence of four symbols; one of them is “=”.
  • Use standard precedence separately on LHS and RHS.


Concept / Approach:
Test each sequence by inserting the symbols left→right. Only one should produce a true equality.


Step-by-Step Solution:
Option (c): “x − + =” → 2 × 4 − 3 + 4 = 9 Evaluate LHS with precedence: 2 × 4 = 8; then 8 − 3 + 4 = 9 Thus 9 = 9 is true.


Verification / Alternative check:
Other options fail, e.g., “+ × = −” gives 2 + 4 × 3 = 4 − 9 ⇒ 14 = −5 (false).


Why Other Options Are Wrong:
They either locate “=” in a place that makes one side negative while the other is clearly positive, or violate equality under proper precedence.


Common Pitfalls:
Ignoring precedence or inserting symbols out of order (not strictly left→right) leads to incorrect judgments.


Final Answer:
x - + =

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