Thực hiện phép tính một cách hợp lí: c) (1/ 2 ⋅ 5/ 17 − 13/ 14 ⋅ 5 /17 + 15/ 238 )/(− 20/ 68 + 26 /14 ⋅ 5 /17 − 5/ 119) .

c) \[\frac{{\frac{1}{2}.\frac{5}{{17}} - \frac{{13}}{{14}}.\frac{5}{{17}} + \frac{{15}}{{238}}}}{{\frac{{ - 20}}{{68}} + \frac{{26}}{{14}}.\frac{5}{{17}} - \frac{{15}}{{119}}}}\]\[ = \frac{{\frac{5}{{34}} - \frac{{65}}{{14.17}} + \frac{{15}}{{238}}}}{{ - 2 \cdot \left( {\frac{5}{{34}} - \frac{{65}}{{14.17}} + \frac{{15}}{{238}}} \right)}} =  - \frac{1}{2}\]