4 is the GCF.
Explanation:
4x3=12
4x5=20
5 Isn’t a factor of 12, and 6 isn’t a factor of 20. Each number above doesn’t work, so the greatest common factor of the numbers 12 and 20 must be 4.
First divide both sides by - 5,

Move the constant to the right side of the equation and change its sign (-4 => +4)

Add the numbers,

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I hope that helps you out!!
Any more questions, please feel free to ask me and I will gladly help you out!!
~Zoey
Answer:
88
Step-by-step explanation:
you add all of her scores which is 313
then you divide by 4 to get 78.35
find the amount you need to bring the average up by calculateing different grades