a) $\frac{3}{5}$ = $\frac{6}{10}$ = $\frac{9}{15}$ = $\frac{12}{20}$ = $\frac{15}{25}$ = $\frac{18}{30}$.
b) $\frac{1}{2}$ = $\frac{2}{4}$ = $\frac{3}{6}$ = $\frac{4}{8}$ = $\frac{5}{10}$ = $\frac{6}{12}$.
c) $\frac{54}{72}$ = $\frac{27}{36}$ = $\frac{9}{12}$ = $\frac{3}{4}$ = $\frac{18}{24}$ = $\frac{108}{144}$.
d) $\frac{18}{30}$ = $\frac{9}{15}$ = $\frac{3}{5}$ = $\frac{36}{60}$ = $\frac{54}{90}$ = $\frac{72}{120}$.