1)9b + 6b - 15 = 615 2)17x -x +5x-19 =

Решим 1-ый пример 

1)9b + 6b - 15 = 615;

    15b = 615 - 15;

    15b = 600;

    b = 600 / 15 = 40.

2)17x -x +5x-19 = 170;

    21х = 189;

     x = 9.

3) (x - 23) / 26 = 8;

     х-23 = 8 * 26;

     x - 23 = 208;

      x = 208 + 23 = 231.

4) 1728 / (56-x) = 36;

    (56 - x) = 1728 / 36;

     56 - x = 48;

      x = 56 - 48;

      x = 8.