help quick please !!

Answer:
Option c = [tex]\sqrt[9]{3}[/tex]
Step-by-step explanation:
One side = 18
Bottom side = 18 (equalateral triangle)
we can use phytagorues theorum:
a = the altitude (unknown)
b= one side (half of the bottom side) = 18/2 = 9
c = hypothenus = 18 (given)
a^2 + b^2 = c^2
a^2 + 9^2 = 18^2
a^2 = 18^2 - 9^2
a^2 = 243
a = [tex]\sqrt{243}[/tex] = [tex]\sqrt{ 3 x 3 x 3 x 3 x 3 }[/tex] = [tex]\sqrt[9]{3}[/tex]
I hope im right !!!i