Answer:
By doing it normally as in arithmetic rule
Explanation:
For starter see the following 2 numbers
334, 53
let add them and substract them in arithmetic way
334
+53
------
387
and
334
-53
------
281
here from right to left we add a single number and write it under the line, if the sum is above 1 decimal value the value upto 1 decimal from the very right of that number is written , for example in case of 9+8 that would be 17 so we would write 7 and carry 1, and the oposite of that for subtraction
Just in the same way lets consider the following example
1.23
+0.93
--------
2.16
and
1.23
-0.93
---------
0.30
Add followup question if needed