summing a column

You can do that in Storyline. 

• Insert a Numeric Entry Field for each "row" of the column.

 

• • When you insert a Numeric Entry Field, the program automatically creates a variable to track what is entered. For easier programming and troubleshooting, I suggest you rename those variables (e.g., row1, row2).
  • If you want any of the fields to have specific numbers that can't be changed, set that number as the default value for that field. Also cover the field with a 99% transparent shape. (That will prevent users from clicking into it.)
• Do this to get the sum:
  • Create a number variable.
  • Insert a text box with a reference to that variable.
  • Create a button with triggers that do this:
    • Set the value of the number variable to 0. 
    • Add the value of the numeric-entry variables to the number variable. (You'll need a trigger for each row.)

Rise doesn't have this functionality, but you could insert a Storyline block that has it. 

FYI: Here's more info about variables: https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-work-with-variables