I need help with number 3

Answer:
5√3 or
8.66 to the nearest hundred.
Step-by-step explanation:
Length of each line of the triangle = 30/3 = 10.
The altitude, side and 1/2 base make a right triangle.
So by Pythagoras:
10^2 = 5^2 + h^2 where h = altitude.
h^2 = 100 - 25 = 75
h = √75 = 5√3.