Multiply the whole equation by \(7\).
\[0\times 7\le 3(u-4)\le 1\times 7\]
Simplify.
\[0\le 3(u-4)\le 7\]
Divide the whole equation by \(3\).
\[0\le u-4\le \frac{7}{3}\]
Add \(4\) to the whole equation.
\[4\le u\le \frac{7}{3}+4\]
Simplify.
\[4\le u\le \frac{19}{3}\]
4<=u<=19/3
