77
step-by-step explanation:
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.
the answer would be c