Question 1152782
<pre>

{{{ 2*pi*R = (2/3)pi*R^2 }}}

Cancel factors appearing on both sides:
{{{ cross(2*pi*R) = (cross(2)/3)cross(pi*R)*R }}}
Multiply both sides by 3:
{{{  3 = R }}}

{{{ highlight( R = 3 in) }}}