easiest way to subtract numbers

Question

I would like to subtract 2 numbers in this line and have the result at the end of the line, like this example:

numbers ; 20.55  ; 10.55

so I have the result

numbers ; 20.55  ; 10.55  ; -10

What is the easiest way to do this?

Answer 1

awk would be a better tool than sed for this purpose

awk -F\; '{print $0, $3-$2}' OFS=" ; "

Example

$ awk -F\; '{print $0, $3-$2}' OFS=" ; " input
numbers ; 20.55 ; 10.55 ; -10