Verified Answer :

  • 8 then -3

    To get this answer identify what operation you are using like addition, subtraction or both. Then see what numbers fit in with the numbers

Your answer is add 8, then subtract 3 because 29 - 21 = 8, so your adding 8, then 29 - ? = 26, the ? is 3, so subtracting 3, so you get add 8, subtract 3.
Glad I could help, and good luck. :)