Question

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

Answer 1

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 

Answer 2

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

$21-2y=9-6y$

$6y-2y=9-21$

$4y=-12$

$y=-12:4$

$y=-3$

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$5\cdot(-3)+7\cdot(3-(-3))=3\cdot(5-2\cdot(-3))-6$ (это проверка)

$-15+7\cdot(3+3)=3(5+6)-6$

$-15+7\cdot6=3\cdot11-6$

$-15+42=33-6$

$27=27$

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$7y-4(3y+5)=2-3(4y-9)$

$7y-12y-20=2-12y+27$

$-5y-20=29-12y$

$12y-5y=29+20$

$7y=49$

$y=49:7$

$y=7$

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$7\cdot7-4\cdot(3\cdot7+5)=2-3\cdot(4\cdot7-9)$

$49-4\cdot(21+5)=2-3\cdot(28-9)$

$49-4\cdot26=2-3\cdot19$

$49-104=2-57$

$-55=-55$