Вычислить 2-3 1\7 (2-1 9/11) :8/ 21

Решите задачу:

$2- 3\frac{1}{7}(2-1 \frac{9}{11}): \frac{8}{21}; 3\frac{1}{7}= \frac{22}{7}; 1\frac{9}{11}= \frac{20}{11}; (2-1 \frac{9}{11})=( \frac{22}{11}- \frac{20}{11})= \frac{2}{11};$ $2) \frac{22}{7}* \frac{2}{11}= \frac{4}{7}; 3) \frac{4}{7} : \frac{8}{21}= \frac{4}{7} * \frac{21}{8} = \frac{3}{2}; 4) 2- \frac{3}{2} = \frac{4}{2} - \frac{3}{2} = \frac{1}{2} =0.5$