\(a)\) \(\frac{1}{28} \times 14=\frac{7}{29}\)

\(b)\) \(\frac{1}{28} \times 2=\frac{1}{14} \times \frac{7}{7}=\frac{7}{98}\)

\(c)\) \(\frac{1}{108} \times 1=\frac{1}{108} \times \frac{7}{7}=\frac{7}{756}\)

\(d)\) \(\frac{1}{18} \times 3=\frac{1}{6} \times \frac{7}{7}=\frac{7}{42}\)