Please explain I have an exam in a bit

it would take 5 hours i think idk i'm not that good at math.can you me with my questions i need asap.

the answer is 11.2 (i know i’m late)

first, you divide the triangle in two, tô form a retangle triangle. after, using pythagoream theorem:

18^2 = 14^2 + (x/2)^2

(x^2/4) + 196 = 324

x^2/4 = 324 - 196

x^2/4 = 128

x^2 = 512

x = √512

x = √2^9

x = 16√2 cm

i hope i you.