Related Clues:

• Put these three with those eight
• Do "sum" math?
• Use a sign
• Do really basic math
• Use an abacus, perhaps
• Count this with that
• Do "sum" calculations
• Sum things up
• Calculate the sum of
• Solve a KenKen puzzle, say
• Do first-grade math
• "This doesn't ___ up"
• Count and combine