15

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Across
  1. 1. - Perfectly round solid.
  2. 4. - Solid with circular bases.
  3. 6. - Math rule written with symbols.
  4. 7. - Proven math rule.
Down
  1. 2. - Math assumption.
  2. 3. - Step-by-step process.
  3. 5. - Solid with six equal faces.