To solve for \( u \) in the equation
\[ -2.2 = \frac{u}{3} + 2.6, \]
follow these steps:
- Isolate the term with \( u \): Subtract \( 2.6 \) from both sides of the equation:
\[ -2.2 - 2.6 = \frac{u}{3}. \]
This simplifies to:
\[ -4.8 = \frac{u}{3}. \]
- Multiply both sides by 3 to solve for \( u \):
\[ u = -4.8 \times 3. \]
Calculating the right side:
\[ u = -14.4. \]
So, the solution is
\[ \boxed{-14.4}. \]