Addition and Subtraction - Balance Equations - within 20

Consider the equation:

12 + 2 = 17 – __

Let's identify the missing number that makes the equation true.

To identify the missing number, first we need to add 12 + 2:
 

12 + 2 = 17 – __
 

14 = 17 – __
 

Now, let’s look for the number which when subtracted from 17 gives 14.
 

14 = 17 – 3
 

12 + 2 = 17 – 3

So, the missing number is 3.