Can someone please explain this real quick so I can get a better understanding on this? My teacher didn't do a good job..

Answer:
[tex]\ \\ \\ \sqrt{113}=c[/tex]
Step-by-step explanation:
Use the Pythagorean theorem as the triangle is a right triangle (90 degree angle is present)Your formula is set as
[tex]a^{2}+b^{2}= c^{2} \\\\7^{2}+8^{2}= c^{2} \\\\64+49= c^{2} \\\\113=c^{2\\\\\\\\\[/tex]