If \(W\) is directly proportional to \(U\), it means that there is a constant of proportionality \(k\) such that \(W = kU\).

Given that \(W = 5\) when \(U = 3\), we can find \(k\) as follows:

\(k = \frac{W}{U} = \frac{5}{3}\)

Now that we have the value of \(k\), we can use it to find \(U\) when \(W = \frac{2}{7}\):

\(W = kU\)

\(\frac{2}{7} = \frac{5}{3} \cdot U\)

Solve for \(U\):

\(U = \frac{\frac{2}{7}}{\frac{5}{3}} = \frac{2}{7} \cdot \frac{3}{5} = \frac{6}{35}\)

So, the value of \(U\) when \(W = \frac{2}{7}\) is 6/35.