Respuesta :

Answer:  B) 20

Work Shown:

[tex]a^2 + b^2 = c^2\\\\b^2 = c^2 - a^2\\\\b = \sqrt{c^2 - a^2}\\\\b = \sqrt{29^2 - 21^2}\\\\b = \sqrt{841-441}\\\\b = \sqrt{400}\\\\b = 20\\\\[/tex]

I applied the pythagorean theorem.
x^2+b^2=c^2

21^2+b^2=29^2

441+b^2=841

b^2=400

sqrt 400=20

b=20