Could someone answer the question with the photo linked below?

Answer:
[tex] \sqrt{28} [/tex]
Step-by-step explanation:
Let's pretend the empty, white space in the middle is a triangle. A right triangle. then we just use the pythogerean theorem to get the a.
[tex] \sqrt{a \:} \: equals \: {8}^{2} - {6}^{2} [/tex]