Skill 3E
Simple Algebra: Subtraction

Here, we are teaching how to use the opposite operation and fact families to solve a horizontal subtraction problem. This is really the same as "counting-up" to find the answer and the preferred method for this type of problem.

 

12 7 =
         
         
7 + = 12
         
         

15 9 =
         
         
9 + = 15