3\frac{1}{3}+12\frac{7}{8}+4\frac{5}{6}=3\frac{8}{24}+12\frac{21}{24}+4\frac{20}{24}=19\frac{49}{24}=21\frac{1}{24}
b)
5\frac{4}{5}+20\frac{3}{8}+135\frac{9}{20}+18\frac{1}{4}=5\frac{32}{40}+20\frac{15}{40}+135\frac{18}{40}+18\frac{10}{40}=178\frac{75}{40}=179\frac{35}{40}=179\frac{7}{8}
c)
1\frac{7}{8}+4\frac{1}{3}-3\frac{1}{6}=1\frac{21}{24}+4\frac{8}{24}-3\frac{4}{24}=5\frac{29}{24}-3\frac{4}{24}=2\frac{25}{24}=3\frac{1}{24}
d)
19\frac{3}{5}-2\frac{1}{2}-6\frac{4}{5}=19\frac{6}{10}-2\frac{5}{10}-6\frac{8}{10}=18\frac{16}{10}-2\frac{5}{10}-6\frac{8}{10}=16\frac{11}{10}-6\frac{8}{10}=10\frac{3}{10}
e)
100\frac{3}{4}+61\frac{7}{20}-73\frac{4}{15}=100\frac{45}{60}+61\frac{21}{60}-73\frac{16}{60}=88\frac{50}{60}=88\frac{5}{6}
f)
54\frac{1}{7}-19\frac{5}{9}-7\frac{1}{3}=54\frac{9}{63}-19\frac{35}{63}-7\frac{21}{63}=53\frac{72}{63}-19\frac{35}{63}-7\frac{21}{63}=27\frac{16}{63}