Two angles are complementary if their sum is 90 degrees. Give that the two complementary angles are 2x - 6 and 6x - 8, it means that
2x - 6 + 6x - 8 = 90
2x + 6x - 6 - 8 = 90
8x - 14 = 90
8x = 90 + 14 = 104
x = 104/8
x = 13
The first angle, 2x - 6 is
2*13 - 6 = 26 - 6 = 20 degrees
The second angle, 6x - 8 is
6 * 13 - 8 = 78 - 8 = 70
The angles are 20 and 70 degrees
