Respuesta :

Answer:

The answer is 29.

Step-by-step explanation:

The steps to do this :

[tex] {c}^{2} = {20}^{2} + {21}^{2} [/tex]

[tex] {c}^{2} = 841[/tex]

[tex]c = \sqrt{841} [/tex]

[tex]c = 29[/tex]