What value of u is a solution to this equation?

To find the value of \( u \) that solves the equation \( 10u - 6u = 36 \), we first simplify the left side:

\[ 10u - 6u = 4u \]

Now, we can rewrite the equation as:

\[ 4u = 36 \]

Next, we can solve for \( u \) by dividing both sides by 4:

\[ u = \frac{36}{4} = 9 \]

Thus, the solution is:

\[ \boxed{9} \]