a) 2/3/5 * 1/1/4 + 5/2
= $\frac{13}{5}$ * $\frac{5}{4}$ + $\frac{5}{2}$
= $\frac{13}{4}$ + $\frac{5}{2}$
= $\frac{13}{4}$ + $\frac{10}{4}$
= $\frac{23}{4}$
= 5/3/4
b) 16/6 : 2/1/6 : 1/1/7
= $\frac{16}{6}$ : $\frac{13}{6}$ : $\frac{8}{7}$
= $\frac{16}{6}$ * $\frac{6}{13}$ *$\frac{7}{8}$
= $\frac{14}{13}$
= 1/1/13
c, 1/3/5 : 8/27 * 5/3
= $\frac{8}{5}$ : $\frac{8}{27}$ * $\frac{5}{3}$
= $\frac{8}{5}$ * $\frac{27}{8}$ * $\frac{5}{3}$
= 9
d, 2/1/3 + 1/3/5 * 5/9
= $\frac{7}{3}$ + $\frac{8}{5}$ * $\frac{5}{9}$
= $\frac{7}{3}$ + $\frac{8}{9}$
= $\frac{21}{9}$ + $\frac{8}{9}$
= $\frac{29}{9}$
=3/2/9