You can put this solution on YOUR website! It could be off by 12.6, or the decimal point could have been put in the wrong place.
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I don't think the question is reasonable.
You can put this solution on YOUR website! 12.6 inches implies that the measurement is accurate to 1 decimal place. It is saying that the quantity is between 12.55 and 12.65 inches. These two are known as the UPPER BOUND and the LOWER BOUND of the number. The greatest error is therefore 0.05 inches in this case.