Answer: [tex]x=5\sqrt{3}[/tex]
Step-by-step explanation:
As the triangle is equilateral, we know that all sides have a length of 10. Thus, if we consider either of the right triangles, we know they have legs of lengths 5 and x (since an altitude of an equilateral triangle bisects the side it is drawn to), and a hypotenuse of 10.
Thus, by the Pythagorean theorem,
[tex]5^{2}+x^{2}=10^{2}\\\\25+x^{2}=100\\\\x^{2}=75\\\\\boxed{x=5\sqrt{3}}[/tex]
