Related Clues:

• Arithmetic directive
• Use a plus sign
• Fire a gun
• Mention as an afterthought
• Calculate sums
• Do some simple calculating
• 'Dang it!'
• Do a summer's work?
• "Ask away!"
• Compute, sometimes
• Write, as a P.S.
• Offer as a bonus
• Make a contribution
• Write in a postscript, e.g.
• Use a '+'