\(\frac{1}{4}+\frac{7}{15} = \frac{15+28}{60} = \frac{43}{60}\). Числитель: 43.
2)\(3\frac{4}{21}-2\frac{5}{14} = \frac{67}{21}-\frac{33}{14} = \frac{134-99}{42} = \frac{35}{42} = \frac{5}{6}\). Числитель: 5.
3)\(1\frac{23}{44}:\frac{16}{67} = \frac{67}{44}\cdot\frac{67}{16} = \frac{4489}{704}\). Числитель: 4489.
4)\(\frac{9}{16}:2\frac{4}{7} = \frac{9}{16}:\frac{18}{7} = \frac{9}{16}\cdot\frac{7}{18} = \frac{1}{16}\cdot\frac{7}{2} = \frac{7}{32}\). Числитель: 7.
5)\(\frac{5}{6}+2\frac{1}{4}\frac{2}{33} = \frac{5}{6}+\frac{9}{4}\frac{2}{33} = \frac{5}{6}+\frac{3}{2}\frac{1}{11} = \frac{5}{6}+\frac{3}{22} = \frac{55+9}{66} = \frac{64}{66} = \frac{32}{33}\). Числитель: 32.
6)\(3\frac{2}{5}:\frac{7}{51}-\frac{5}{21} = \frac{17}{5}\cdot\frac{51}{7}-\frac{5}{21} = \frac{17\cdot 51}{35}-\frac{5}{21} = \frac{867}{35}-\frac{5}{21} = \frac{2601-25}{105} = \frac{2576}{105}\). Числитель: 2576.