The length of the other leg is 16.5 cm.
In order to determine the length of the other leg, Pythagoras theorem would be used.
The Pythagoras theorem: a² + b² = c²
where
21² - 13²
441 -169
√272 = 16.5cm
To learn more about Pythagoras theorem, please check: https://brainly.com/question/14580675