To solve for \( \frac{5}{16} - p \) when \( p = \frac{3}{8} \), we can substitute \( p \) with \( \frac{3}{8} \):
\[ \frac{5}{16} - \frac{3}{8} \]
Next, we need a common denominator to subtract the two fractions. The denominator of \(\frac{5}{16}\) is \(16\), and the denominator of \(\frac{3}{8}\) is \(8\). The least common denominator (LCD) of \(16\) and \(8\) is \(16\).
We'll convert \(\frac{3}{8}\) to a fraction with a denominator of \(16\):
\[ \frac{3}{8} = \frac{3 \times 2}{8 \times 2} = \frac{6}{16} \]
Now we can perform the subtraction:
\[ \frac{5}{16} - \frac{6}{16} = \frac{5 - 6}{16} = \frac{-1}{16} \]
Thus,
\[ \frac{5}{16} - \frac{3}{8} = -\frac{1}{16} \]
The final answer is:
\[ -\frac{1}{16} \]