\[u = |3 - v|\]
\[v = - 25:\]
\[u = \left| 3 - ( - 25) \right| = |3 + 25| =\]
\[= |28| = 28.\]
\[v = 0:\]
\[u = |3 - 0| = |3| = 3.\]
\[v = 4:\]
\[\ u = |3 - 4| = | - 1| = 1.\]