The question is in the picture.

Answer:
x = 7[tex]\sqrt{3}[/tex]
Triangle area formula: base * height * 1/2
We are given:
Base - 14 cm
Height - x
Using the pythagorean theroem (a^2 + b^2 = c^2) we can figure out the height.
We are given:
Side a - 14 / 2 = 7 cm
Side b - the height (x)
Side c - 14 (it's an equilateral triangle)
Now, substitute the given values:
7^2 + x^2 = 14^2
49 + x^2 = 196
x^2 = 147
x = [tex]\sqrt{147}[/tex]
x = 7[tex]\sqrt{3}[/tex]