Related Clues:

• Hook up with, on Facebook?
• Combine numbers
• Mix (in)
• Build on, with 'to'
• Do some sums
• Tack on a few extra
• Check a check
• Run numbers?
• "Just ___ water"
• Write in a postscript, e.g
• Tally up again
• Bring numbers together
• Mention parenthetically
• Focusing problem, for short
• Check your arithmetic