I really don’t understand it.

Answer:
11.1803399
Step-by-step explanation:
By Pythagoras Theorem
[tex] \sqrt{hight {}^{2} + base {}^{2} } [/tex]
[tex] \sqrt{100 + 25} [/tex]
[tex] \sqrt{125} [/tex]
[tex] = = > 11.1803399[/tex]
Answer By,
Zeeshan Khan