#### Answer

Right Triangle

#### Work Step by Step

Using the Pythagorean Theorem...
$a^{2}+b^{2}=c^{2}$
$20^{2}+21^{2}=29^{2}$
Simplify...
$400+441=841$
$841=841$
Since the sum of the sides squared $(841)$ is equal to the hypotenuse squared $(841)$, the triangle is a right triangle.