Can someone help me on this question and explain the process

Answer:
Step-by-step explanation: Use Pythagorean Theorem
[tex]a^2 + b^2 = c^2\\[/tex]
[tex]15^2 + b^2 = 9^2\\[/tex]
[tex]225 + b^2 = 81[/tex]
[tex]- 255[/tex] [tex]-255[/tex]
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[tex]b^2 = 174\\[/tex]
[tex]b^2 = \sqrt{-174}[/tex]