Номер 167. Помогите решить пожалуйста )

Решите задачу:

$a)|\frac{7}{12}-\frac{1}{4}|=|\frac{4}{12}|=\frac{1}{3}\\\\b)|\frac{2}{3}|-|-\frac{4}{9}|=\frac{2}{3}-\frac{4}{9}=\frac{2}{9}\\\\c)|-\frac{7}{8}|-|+\frac{1}{4}|=\frac{7}{8}-\frac{1}{4}=\frac{5}{8}\\\\d)|-\frac{17}{21}|-|\frac{3}{7}|=\frac{17}{21}-\frac{3}{7}=\frac{8}{21}\\\\e)|\frac{19}{25}|-|\frac{4}{5}|=\frac{19}{25}-\frac{4}{5}=\frac{19-20}{25}=-\frac{1}{25}\\\\f)|-\frac{17}{30}|-|\frac{1}{6}|=\frac{17}{30}-\frac{1}{6}=\frac{12}{30}=\frac{2}{5}$