To solve the equation \( 21x + 1,998 = 2,243 \), you can start by isolating \( x \).
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Subtract \( 1,998 \) from both sides: \[ 21x = 2,243 - 1,998 \] \[ 21x = 245 \]
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Now, divide by \( 21 \): \[ x = \frac{245}{21} \]
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Calculate the value of \( x \): \[ \frac{245}{21} \approx 11.67 \]
Now, among the given options (100, 1,000, 1, 10), the best estimate for \( x \) would be \( 10 \).
So the final answer is: 10