5y+7(3-y)=3(5-2y)-6-это первый. 7y-4(3y+5)=2-3(4y-9)

5y+7(3-y)=3(5-2y)-6

5y+21-7y=15-6y-6

5y-7y+6y=15-6-21

4y= -12

y=-12:4

у= - 3

7у-4(3у+5)=2-3(4у-9)

7у-12у-20=2-12у+27 

 7у-12у+12у=20+2+27

7у= 49

у=49:7

у=7 

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(это проверка)

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