Вправи: 868

868. Розв’яжи рівняння.

a) 7(4 – t) + 3(t – 5) = 9t;

28 – 7t + 3t – 15 = 9t;

–4t – 9t = 15 – 28;

–13t = –13|: (–13);

t = 1.

б) 3(x + 1,5) + 2(3 + x) = –5;

3x + 2x = –5 – 4,5 – 6;

5x = –15,5|: 5;

x = –3,1.

в) 5(3 – 2x) – (12 – 7x) = 0;

15 – 10x – 12 + 7x = 0;

–3x = 12 – 15;

–3x = –3|: (–3);

x = 1;

г) 5z + 2(4 + z) = 3z + 28;

5z + 8 + 2z = 3z + 28;

7z – 3z = 28 – 8;

4z = 20|: 4;

z = 5.