Let's begin by expanding both sides of the equation:

3(5 + 12x) - (6x - 1)(6x + 1) = 2.5x

Simplifying:

15 + 36x - (36x^2 - 1) = 2.5x

Now distribute the negative sign inside the brackets:

15 + 36x - 36x^2 + 1 = 2.5x

Combine like terms:

36x - 36x^2 + 16 = 2.5x

Rearrange to set the equation equal to 0:

36x - 36x^2 + 16 - 2.5x = 0

Now combine like terms again:

-36x^2 + 33.5x + 16 = 0

This is a quadratic equation. To solve for x, you can use the quadratic formula:

x = (-b ± √(b^2 - 4ac)) / 2a

In this case, a = -36, b = 33.5, and c = 16. Plug these values into the quadratic formula to find the solutions for x.