Answer:
B. 5
Step-by-step explanation:
Use the pythagorean theorem to solve: [tex]a^{2}[/tex]+[tex]b^{2}[/tex]=[tex]c^{2}[/tex].
[tex]a^{2}[/tex]+[tex]12^{2}[/tex]=[tex]13^{2}[/tex]
[tex]a^{2}[/tex]+144=169
Subtract 144 from 169.
[tex]a^{2}[/tex]-144=169-144
[tex]a^{2}[/tex]=25
Square root to get a.
[tex]\sqrt{a}[/tex]=[tex]\sqrt{25}[/tex]
a= 5
