How do you simplify #0.6+5.8#?
Simple addition is a bit hard to explain, but the easiest way to do it is column addition and drop-down from there.
Line up the decimals of all decimal-inclusive numbers you wish to add together, like so:
And add the numbers from there.
The 4 gets dropped down, while the '10' gets carried over as a 1 to the next level over towards the left. In this case, the decimal was in the tenths place, so it goes immediately to the ones, prior to the decimal.
Don't forget to re-add the decimal once you're done.