Answer:
you get the wrong answer
Explanation:
The purpose of aligning the decimal points is to make sure that you're adding and subtracting values that have the same place value (and carrying or borrowing appropriately). Aligning the decimal points makes this easier.
If you pay attention to place value, the location of the decimal point is immaterial. It could even be on another sheet of paper or computer screen. Of course, a calculator takes care of place value automatically, if you enter the numbers correctly.
If you don't align the decimal points, you risk making an error in the computation.