г) $$8\frac{1}{12} - 3\frac{4}{15} - 1\frac{7}{30} = 8\frac{5}{60} - 3\frac{16}{60} - 1\frac{14}{60} = 8\frac{5}{60} - (3\frac{16}{60} + 1\frac{14}{60}) = 8\frac{5}{60} - 4\frac{30}{60} = 8\frac{5}{60} - 4\frac{1}{2} = 8\frac{5}{60} - 4\frac{30}{60} = 7\frac{65}{60} - 4\frac{30}{60} = 3\frac{35}{60} = 3\frac{7}{12}$$.
Ответ: $$3\frac{7}{12}$$