Count total parts in the rectangle. Find how many should be red for \( \frac{1}{3} \). Subtract from the number currently red to find how many to erase.<br><br>
• Count the total number of equal parts in the rectangle.<br>
• Multiply the total parts by \( \frac{1}{3} \) to find how many should be red.<br>
• Count the currently red parts and subtract the target.<br>
• Parts to erase = 5<br>
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Final Answer: C: 5