You want to use the addition property, so you need to ADD each term. Just change the minuses to pluses, making sure you keep the negative with the number
5x-8x-7y+y =
5x + -8x + -7y +y
Answer:
B. 
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D , because 28-9=21 and 21=x
Answer:
whats the problem?
Step-by-step explanation: