Work Step by Step
Now to make it easy we start by turning 39,45 into an even number $\approx 40$ $863,2-40=823,2$ At this point you can completly ignore whatever is after the comma. After that we subtract 39,45 from 40, which is 0,55. That is the amount we did not the to subtract but did to make it easier. To undo this we add it back in. $823,2 + 0,55 = 823,75$. And this is the answer.