Answer:
[tex]b = \sqrt{65} [/tex]
Step-by-step explanation:
[tex] {b}^{2} + {4}^{2} = {9}^{2} \\ {b}^{2} + 16 = 81 \\ {b}^{2} = 81 - 16 \\ {b}^{2} = 65 \\ b = \sqrt{65} [/tex]
I hope I helped you^_^
