20 questions / Subtracting Without Regrouping Subtracting With Regrouping 1 Subtracting With Regrouping 2 Subtracting Across Zeros
25 questions / Subtracting Without Regrouping Subtracting With Regrouping in Hundreds and Thousands Subtracting With Regrouping in Ones, Tens, Hundreds, and Thousands Subtracting Across Zeros Subtracting Basics