What is the general rule for adding and subtracting decimals?

The general rule for adding and subtracting decimals is to align the decimals vertically. This ensures that the numbers are properly positioned according to their place values, making it easier to perform calculations accurately. By aligning the decimal points, you can clearly see which digits correspond to the same power of ten, allowing for straightforward addition or subtraction of whole numbers and decimal parts without the risk of misalignment. This method is crucial for maintaining accuracy in calculations, particularly when dealing with numbers of different lengths after the decimal point.