How does 9 and 10 = 21?

The following expressions are possible ways of using 9 and 10 to get 21:

  1. 9 + 10 - 9 + 10 - 9 + 10
  2. ( 9 × 9 ) - 10 - 10 - 10 - 10 - 10
  3. 9 ( 9 + 10 ) - ( 10 × 9 ) - ( 10 × 9 ) + 10 + 10 + 10
  4. 9 + 10
  5. 9 × 10 - 9 + 10 - ( 9 × 10 ) + 10 + 10
  6. 9 + 10 + 10 + 10 - 9 - 9 ( -9 + 10 )

What is the sum of the #s of the 4 expressions that actually equal 21? (Assume the expressions were 1, 4, 5, and 6. Add them all up to get the answer you are looking for.)

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