Tính bằng cách thuận tiện:

a) \(\frac{{1\,\,450}}{{1\,\,000}} - \frac{{700}}{{1\,\,000}} + \frac{{250}}{{1\,\,000}}\)

= \(\frac{{1\,\,450 - 700 + 250}}{{1\,\,000}}\) = \(\frac{{1\,\,000}}{{1\,\,000}}\) = 1

b) \(\frac{{12}}{5} + \frac{7}{{15}} + \frac{4}{{15}}\)

= \(\frac{{36}}{{15}} + \frac{7}{{15}} + \frac{4}{{15}}\) = \(\frac{{36 + 7 + 4}}{{15}} = \frac{{47}}{{15}}\)