2 minus the sum of u

and 6? I just need the equation

To be crystal clear, I'd use parentheses here:

2 - (u + 6). If you wish to simplify that, you'd get 2 - 6 - u, or - 4 - u.

Eventually you'll have to know how to do these problems yourself, so I'd suggest you stop writing, "I just need the equation." You need the know-how.