Answer: 
Step-by-step explanation:
1. By definition, the associative property of addition is:

This property says that you can group the numbers in different ways and you will obtain the same result.
2. Therefore, if you have the following expression:

You apply the Asociative property of addition by regrouping the numbers as following:

3. Then, you can conclude that the correct option is B.
| 42 | The absolute value of forty two
We can identify that the missing reason in the proof is: Definition of Congruent angles.
<h3>How to give proof of a congruent triangle?</h3>
We know that an angle measure of 90° of ∠ABC in the triangle means that it is a right angle triangle.
We also see that ∠ADB is also a right angle and is equal to 90°.
Now, since they have exactly the same measure, these angles are congruent. Then we can say that the angles are congruent and as such:
∠ABC ≅ ∠ABD
Thus, we can identify that the missing reason is: Definition of Congruent angles.
Read more about Triangle proof at; brainly.com/question/1248322
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Answer:
what expression
Step-by-step explanation: