Question

Question was provided via image upload.

Explanation:

Step1: Isolate \( u \)

To solve for \( u \) in the equation \( s = u + t \), we need to get \( u \) by itself. We can do this by subtracting \( t \) from both sides of the equation.

$$ s - t = u + t - t $$

Step2: Simplify the equation

Simplifying the right - hand side, \( t - t = 0 \), so we are left with:

$$ u=s - t $$

Answer:

\( s - t \)