1) -6/7x = -9;

Ищем неизвестный множитель:

x = -9 : (-6/7);

x = 9 * 7/6;

x = 10.5;

2) -8 * 2/3 + 4x = 6;

-16/3 + 4x = 6;

4x = 6 + 16/3;

4x = 34/3;

x = 34/3 * 1/4;

x = 34/12;

x = 2 5/6.