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

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.
Answer:
-21=24
Step-by-step explanation:
Subtract 24 from 3
-21=8+2^2
Raise 4 to the power of 2
-21=8+16
Add 8 and 16
-21=24
Answer: The height of the tree will be 21 meters
Answer:

Step-by-step explanation:

20 can be written as a product of 4 and 5.

4 is a perfect square.

Square root of 4 is 2.

I think its 149/ 490. Not sure, but pretty confident. Hope this helps.