What is the least common denominator of 2/3 and 5/7?

$\frac{14}{21} + \frac{15}{21} = \frac{29}{21} \mathmr{and} 1 \frac{8}{21}$
$\frac{15}{21} - \frac{14}{21} = \frac{1}{21}$
$\frac{14}{21} \times \frac{15}{21} = \frac{10}{21}$
$\frac{14}{21} \div \frac{15}{21} = \frac{14}{15}$