1)
is simplified into 
2)
is simplified into 
3)
is simplified into 
4)
is simplified into 
5)
is simplified into 
Step-by-step explanation:
We need to solve the polynomials.
1) 
Solving:

So,
is simplified into 
2) 
Solving:

Expanding:

So,
is simplified into 
3) 
Solving:

Expanding:

So,
is simplified into 
4) 
Solving:

Expanding:

SO,
is simplified into 
5) 
Solving:

Expanding:

So,
is simplified into 
Keywords: Solving Polynomials
Learn more about solving Polynomials at:
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Brainly is erroneously preventing my response from being posted due to nonexistent profanity or links. So, I have converted my answer into an image file, which I have attached. I also attached an annotated diagram of the figure in the image you posted. Please let me know if you have trouble accessing either. Hope this helps.
Answer:
X = 5
Step-by-step explanation:
28 = 7x + 3 - 2x
28 = 5x + 3
28 - 3 = 5x + 3 - 3
25 = 5x
25/5 = 5x/5
X = 5
The independent variable, x, represents the SIDE LENGTHS, and the dependent variable is the PERIMETER, because the PERIMETER, depends on the SIDE LENGTHS.