Question: xslt how to sum values?
Answer: Name. sum() Function — Converts all nodes in the argument node-set to numbers, and then returns the sum of all of those numbers. ... 
Synopsis. number sum( node-set )
Inputs. A node-set. ... 
Output. The sum of the numeric values of all of the nodes in the argument node-set. ... 
Defined in. ... 
Example.