Question 112729
This is a Pythagorean Theorem problem.

Draw a right triangle with 8 as the vertical leg, 6 as the horizontal leg, and x as the hypotenuse:
 

{{{6^2+8^2=x^2}}}
{{{36+64=x^2}}}
{{{100=x^2}}}
{{{10=x}}}

Hope this helps!