Answer:
[tex]\sqrt{144}[/tex]
Step-by-step explanation:
[tex]15^{2}[/tex] = [tex]x^{2} + 9^{2}[/tex]
[tex]x^{2} = 15^{2} - 9^{2} \\x^{2} = 144\\x = \sqrt{144}[/tex]
