Question 713956
Clear the denominators and work with the result until the equation is in the form of a quadratic equation.


Lowest common denominator to begin is {{{2*3*r^2.}}}.

{{{1/(2 r^2)= 1/(6  r)-2/3}}}
{{{(1/(2 r^2))2*3*r^2= (1/(6  r)-2/3)2*3*r^2}}}
..
That's how you start.  Can you continue and then finish?