Nối phép tính đúng: 3/30 + 5/30 + 7/30

Giải thích

\[\frac{3}{{30}} + \frac{5}{{30}} + \frac{7}{{30}} = \frac{{3 + 5 + 7}}{{30}} = \frac{{15}}{{30}} = \frac{1}{2}\]
\[\frac{{70}}{{84}} - \frac{9}{{84}} - \frac{5}{{84}} = \frac{{70 - 9 - 5}}{{84}} = \frac{{56}}{{84}} = \frac{2}{3}\]

\[\frac{{25}}{{36}} - \frac{7}{{36}} - \frac{9}{{36}} = \frac{{25 - 7 - 9}}{{36}} = \frac{1}{4}\]

\[\frac{{15}}{{75}} + \frac{{25}}{{75}} + \frac{{20}}{{75}} = \frac{{15 + 25 + 20}}{{75}} = \frac{4}{5}\]