Hello there! :)
Answer:
1. B. 8. and x=8
*The answer must have a positive sign.*
2. D. Infinitely many.
3. D. -1 and y=-1
*The answer must have a negative sign.*
4. C. He didn't add 13 to 26.
5. B. 4 and y=4
*The answer must have a positive sign.*
Explanation:
1. First, you divide by 5 from both sides of an equation.

Then, simplify.

Answer: →

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2. 4x=4x both sides are equal and it's true.
Answer:

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3. First, switch sides of an equation.

Then, you subtract by 9 from both sides of an equation.

Simplify and solve.

Answer: →

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4. First, add by 13 from both sides of an equation.

Then simplify and solve.

Answer:
and

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5. First, subtract by 9 from both sides of an equation.

Then simplify and solve.

Answer:

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Hope this helps!
Thanks!
-Charlie
Have a great day!
:)