59 is a tough bird to deal with; its only factors are 1 and 59.
Thus, forget about factoring.  Instead, use the quadratic formula, or solve the equation by completing the square.
Please note:  x2 is ambiguous.  Please write x^2 to indicate "the square of 2."
Here you have 1x^2 - 12x + 59 = 0, for which a=1, b=-12 and c=59.
Use the quadratic formula:  x=[-b plus or minus sqrt(b^2-4ac)] / (2a)
to find the two roots.  Notice that the "discriminant" b^2 - 4ac will be negative, meaning that your two roots will be "complex."
        
             
        
        
        
Answer:
d=8.0 meters
Step-by-step explanation:
The volume of a cone is given by
V = 1/3 pi r^2 h
We are given the volume and the height
117.23 and the height 7
117.23 = 1/3 *3.14 *r^2 * 7
117.23 = 7.3266666666 *r^2
Divide each side by 7.3266666666
117.23/7.3266666666 = 7.3266666666 *r^2/7.3266666666 
16.00045496 = r^2
Take the square root of each side
sqrt(16.00045496) =sqrt( r^2)
4.000 = r
We found the radius but it wants the diameter
d = 2*r
d =2*4.0
d=8.0 meters