Answer:
x = 21
Step-by-step explanation:
Pythagoras' theorem,
[tex] {29}^{2} = {x}^{2} + {20}^{2} [/tex]
[tex] {x}^{2} = {29}^{2} - {20}^{2} = 441 [/tex]
[tex]x = 21[/tex]
