Answer:
[tex]a=12[/tex]
Step-by-step explanation:
Pythagorean Theorem: [tex]a^{2}+b^{2}=c^{2}[/tex]
In this case, a = 9, b = a, and c = 15.
[tex]9^{2}+a^{2}=15^{2}[/tex]
[tex]81+a^{2}=225[/tex]
The, we subtract 81 from both sides getting:
[tex]a^{2}=144[/tex],
Then, [tex]a=12[/tex]
