Answer:
Associative and commutative properties of addition
Explanation:
The one thing that the associative property of addition says that
![(a+b)+y=a+b+y](https://img.qammunity.org/2023/formulas/mathematics/college/shavuc6yfp5t0i6wyjglmlhajqw9z8jj9c.png)
and the commutative property of addition says
![a+b=b+a](https://img.qammunity.org/2023/formulas/mathematics/college/hsu1x18584pvvkbyu47y72cp747tlzkr7d.png)
(the order of addition does not matter )
Now, the steps we take to solve our equation are the following:
![\begin{gathered} \mleft(3x+4y\mright)+5x=8x+4y \\ 3x+4y+5x=8x+4y\text{ (the associative property of addition )} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/avu4daf9l0ny47egjxwey73485puhxxsge.png)
The second step is
![\begin{gathered} 3x+4y+5x=8x+4y\text{ } \\ 3x+5x+4y=8x+4y\text{ (commutative property of addition.)} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/jynd4twroalm4aiflhodihpmef5enq51e1.png)
which simplifies to
![\begin{gathered} 8x+4y=8x+4y \\ 4y=4y \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/bjgct3myhsb357lb752o3nxs6xs29b8usn.png)
Hence, we used associative and commutative properties of addition to solve our equation.