3 please help me pls

Answer:
The answer is 7.48.
Step-by-step explanation:
[tex]c^{2} - b^{2}[/tex] = [tex]a^{2}[/tex]
[tex]15^{2} - 13^{2} = a^{2}[/tex]
[tex]225 - 169[/tex] = [tex]a^{2}[/tex]
[tex]56 = a^{2}[/tex]
[tex]\sqrt{56} = \sqrt{a^{2} }[/tex]
[tex]7.48 = a[/tex]