Tính: \(\frac{9}{{15}} + \frac{{ - 1}}{{25}} + \frac{{ - 7}}{{20}}\)

* Hướng dẫn giải

\(\frac{9}{{15}} + \frac{{ - 1}}{{25}} + \frac{{ - 7}}{{20}} = \frac{3}{5} + \frac{{ - 1}}{{25}} + \frac{{ - 7}}{{20}} = \frac{{3.20 - 1.4 - 7.5}}{{100}} = \frac{{60 - 4 - 35}}{{100}} = \frac{{21}}{{100}}\)

Chọn C.