Решите уравнения: а) 7(2 + у) - 3у = 5у - 6 б) 4х - 2(3 + х) = 9 - х г) -3(5а - 1) +4а = 2а + 7(5 - 3а)

а) 

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(это проверка)

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б) 

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г) 

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

14+7y-3y=5y-6;

14+4y=5y-6;

4y-5y=-6-14;

-y=-20;

y=20!

б) 4x-2(3+x)=9-x;

4x-6-2x=9-x;

2x-6=9-x;

2x+x=9+6;

3x=15;

x=5!

г) -3(5a-1)+4a=2a+7(5-3a);

-15a+3+4a=2a+35-21a;

-11a+3=-19a+35;

-11a+19a=35-3;

8a=32;

a=32/8;

a=4!