Use fact patterns to complete each equation.
8 + 2 = 10
9 +..... = 10

The correct answer is: 1

>>>We were given that, the sum of addend 8 and augend 2 gives 10.
>>>Similarly, we were asked to find the addend when we add the augend 9 to give the sum 10.
>>>In both cases the sum remains same and the augend is increased by 1 unit. Then, the addend should be decrement by 1 unit.
>>>Therefore, the sum is 9 + 1 = 10. 

8 + 2 = 10
9 + 1 = 10