Решите весь 307 номер

Решите задачу:

$1) \frac{1}{4} + \frac{1}{5} = \frac{5}{20} + \frac{4}{20} = \frac{9}{20} \\ \\ 2) \frac{1}{3} + \frac{1}{7} = \frac{7}{21} + \frac{3}{21} = \frac{10}{21} \\ \\ 3) \frac{3}{5} + \frac{3}{4} = \frac{12}{20} + \frac{15}{20} = \frac{27}{20} =1 \frac{7}{20} \\ \\ 4) \frac{1}{2} + \frac{7}{9} = \frac{9}{18} + \frac{14}{18} = \frac{23}{18} =1 \frac{5}{18} \\ \\ 5) \frac{5}{7} +0= \frac{5}{7} \\ \\ 6) \frac{2}{3} - \frac{2}{5} = \frac{10}{15} - \frac{6}{15} = \frac{9}{15} = \frac{3}{5} \\ \\$

$7) \frac{1}{2} - \frac{1}{3} = \frac{3}{6} - \frac{2}{6} = \frac{1}{6} \\ \\ 8) \frac{3}{5} - \frac{4}{7} = \frac{21}{35} - \frac{20}{37} = \frac{1}{37} \\ \\ 9) \frac{5}{7} - \frac{1}{6} = \frac{30}{42} - \frac{7}{42} = \frac{23}{42} \\ \\ 10) \frac{8}{9} -0= \frac{8}{9} \\ \\ 11) \frac{3}{4} + \frac{4}{5} = \frac{15}{20} + \frac{16}{20} = \frac{31}{20} =1 \frac{11}{20} \\ \\ 12) \frac{3}{4 }+ \frac{2}{9} = \frac{27}{36} + \frac{8}{36} = \frac{35}{36}$