Помогите решить по 21-24 пример !!!!!!→→

$21) 2\frac{4}{100} - 1 \frac{1}{4} = 2\frac{4}{100} - 1 \frac{25}{100} = 1 \frac{104}{100} - 1 \frac{25}{100} = \frac{79}{100} \\ \frac{79}{100} : \frac{1}{20} = \frac{79*20}{100} = \frac{79}{5} = \frac{158}{10} = 15.8 \\ \\ 22) 3 \frac{42}{100} - 2 \frac{5}{8} = 2 \frac{1420}{1000} - 2 \frac{625}{1000} = \frac{795}{1000} \\ \frac{795}{1000} : \frac{1}{50} = \frac{795 * 50}{1000} = \frac{795}{20} = \frac{3975}{100} = 39.75 \\ \\$
$23) 6 \frac{5}{17} + 1 \frac{12}{17} = 8 \\ 4 \frac{2}{5} - 2 \frac{3}{5} = 3 \frac{7}{5} - 2 \frac{3}{5} = 1 \frac{4}{5} \\ 23 : 8 = \frac{23}{8} \\ 1 \frac{4}{5} : 5 = \frac{9}{5 * 5} = \frac{9}{25} \\ \frac{23}{8} - \frac{9}{25} = \frac{23*25 - 8*9}{200} = \frac{575 - 72}{200} = \frac{503}{200} = \frac{2515}{1000} = 2.515 \\$ $24) 7 \frac{4}{13} - 4 \frac{4}{13} = 3 \\ 13 \frac{6}{13} + 11 \frac{7}{13} = 25 \\ 3 : 0.15 = 3 : \frac{15}{100} = 3 * \frac{100}{15} = \frac{300}{15} = 20 \\ 4: 25 = 4 * \frac{1}{25} = \frac{4}{25} \\ 20 - \frac{4}{25} = 20 - \frac{16}{100} = 20 - 0.16 = 19.84$