Simplifying the given expression, we get:

5a(3a-8) - 3b(3a-8) + 9ab(3a-8) - (3a-8)

Expanding each term:

= 15a^2 - 40a - 9ab + 24b + 27a^2b - 72ab - 3a + 8

Combining like terms:

= 15a^2 + 27a^2b - 9ab - 72ab - 3a - 40a + 24b - 3a + 8

= 42a^2 + 18ab - 83a + 24b + 8

Therefore, the simplified expression is 42a^2 + 18ab - 83a + 24b + 8.