The relationship is not proportional because the boys and girls are in different grades and they are in different activities.
Answer:

Step-by-step explanation:
![\left[\begin{array}{ccc}x + 3y = 7\\x - 3y = 7\end{array}\right]](https://tex.z-dn.net/?f=%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Dx%20%2B%203y%20%3D%207%5C%5Cx%20-%203y%20%3D%207%5Cend%7Barray%7D%5Cright%5D)
Isolate
for
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Substitute
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Isolate
for
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For

Substitute 



The solution to the system of equations are:

Hope I helped. If so, may I get brainliest and a thanks?
Thank you. Have a good day! =)
I think it’s either C or D
Muliply 65 and 0.12 and get 7.8
Subtract 65-7.8 to get marked down price
57.2 is the price after markdown
Answer:
14 length of the side is 3x-7
and 15 length of side is 2x+6