Найдите значение выражения: 8-4,2*(2 5/14-1 4/21)

Решите задачу:

$8-4,2( 2\frac{5}{14} - 1 \frac{4}{21} ) = 3 \frac{1}{10} \\1) 2 \frac{5}{14} - 1 \frac{4}{21} = \frac{33}{14} - \frac{25}{21} = \frac{99}{42} - \frac{50}{42} = \frac{49}{42} = \frac{7}{6} = 1 \frac{1}{6} \\2) 4,2*\frac{7}{6} = \frac{42}{10}* \frac{7}{6} = \frac{42*7}{10*6} = \frac{49}{10} = 4 \frac{9}{10} \\3) 8 - 4 \frac{9}{10} = 7 \frac{10}{10}-4 \frac{9}{10} = 3 \frac{1}{10}$